diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..c29d6ab
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,12 @@
+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.{sh,markdown}]
+indent_size = 4
\ No newline at end of file
diff --git a/.ruby-version b/.ruby-version
index 276cbf9..437459c 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-2.3.0
+2.5.0
diff --git a/Appraisals b/Appraisals
index e02d8cd..28b94ca 100644
--- a/Appraisals
+++ b/Appraisals
@@ -2,12 +2,10 @@ appraise '40' do
   gem 'rails', '~> 4.0.0'
 end
 
-
 appraise '41' do
   gem 'rails', '~> 4.1.0'
 end
 
-
 appraise '42' do
   gem 'rails', '~> 4.2.0'
 end
@@ -25,5 +23,5 @@ appraise '5.2' do
 end
 
 appraise '6.0' do
-  gem 'rails', '6.0.0.beta3'
+  gem 'rails', '~> 6.0.0'
 end
diff --git a/README.md b/README.md
index f455133..b6b33ba 100644
--- a/README.md
+++ b/README.md
@@ -55,7 +55,7 @@ passing an options hash. The following keys are supported:
 
 `:length` number of characters, defaults to __32__
 
-`:type` type of string, can be one of: `:human`, `:auto`, defaults to __:auto__
+`:type` type of string, can be one of: `:human`, `:numbers`, or `:auto` and defaults to __:auto__
 
 Human type generates strings easier to read by excluding ambiguous characters like `1, 5, 8, B, o, O, I, l, s, u`.
 
@@ -63,6 +63,8 @@ Human type generates strings easier to read by excluding ambiguous characters li
 
 `:scope` scopes, defines the `ActiveRecord` `scope` applied before calculating the `position` field value. Defaults to __[]__
 
+`:chars` Custom character list. If provided then `:type` will be ignored. `:chars` can be a range, an array of characters, or a string of characters.
+
 To generate a unique-random on the fly `Uniqueness.generate` that will produce a random field for you.
 
 You can also pass some options `Uniqueness.generate(type: :human)`.
diff --git a/gemfiles/.bundle/config b/gemfiles/.bundle/config
new file mode 100644
index 0000000..c127f80
--- /dev/null
+++ b/gemfiles/.bundle/config
@@ -0,0 +1,2 @@
+---
+BUNDLE_RETRY: "1"
diff --git a/gemfiles/40.gemfile b/gemfiles/40.gemfile
new file mode 100644
index 0000000..f844fec
--- /dev/null
+++ b/gemfiles/40.gemfile
@@ -0,0 +1,7 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rails", "~> 4.0.0"
+
+gemspec path: "../"
diff --git a/gemfiles/40.gemfile.lock b/gemfiles/40.gemfile.lock
new file mode 100644
index 0000000..35ab684
--- /dev/null
+++ b/gemfiles/40.gemfile.lock
@@ -0,0 +1,123 @@
+PATH
+  remote: ..
+  specs:
+    uniqueness (1.1.1)
+      activerecord (>= 4.0.0)
+      railties (>= 4.0.0)
+
+GEM
+  remote: https://rubygems.org/
+  specs:
+    actionmailer (4.0.13)
+      actionpack (= 4.0.13)
+      mail (~> 2.5, >= 2.5.4)
+    actionpack (4.0.13)
+      activesupport (= 4.0.13)
+      builder (~> 3.1.0)
+      erubis (~> 2.7.0)
+      rack (~> 1.5.2)
+      rack-test (~> 0.6.2)
+    activemodel (4.0.13)
+      activesupport (= 4.0.13)
+      builder (~> 3.1.0)
+    activerecord (4.0.13)
+      activemodel (= 4.0.13)
+      activerecord-deprecated_finders (~> 1.0.2)
+      activesupport (= 4.0.13)
+      arel (~> 4.0.0)
+    activerecord-deprecated_finders (1.0.4)
+    activesupport (4.0.13)
+      i18n (~> 0.6, >= 0.6.9)
+      minitest (~> 4.2)
+      multi_json (~> 1.3)
+      thread_safe (~> 0.1)
+      tzinfo (~> 0.3.37)
+    appraisal (2.2.0)
+      bundler
+      rake
+      thor (>= 0.14.0)
+    arel (4.0.2)
+    builder (3.1.4)
+    concurrent-ruby (1.1.5)
+    coveralls (0.8.23)
+      json (>= 1.8, < 3)
+      simplecov (~> 0.16.1)
+      term-ansicolor (~> 1.3)
+      thor (>= 0.19.4, < 2.0)
+      tins (~> 1.6)
+    diff-lcs (1.3)
+    docile (1.3.2)
+    erubis (2.7.0)
+    i18n (0.9.5)
+      concurrent-ruby (~> 1.0)
+    json (2.2.0)
+    mail (2.7.1)
+      mini_mime (>= 0.1.1)
+    mini_mime (1.0.2)
+    minitest (4.7.5)
+    multi_json (1.13.1)
+    rack (1.5.5)
+    rack-test (0.6.3)
+      rack (>= 1.0)
+    rails (4.0.13)
+      actionmailer (= 4.0.13)
+      actionpack (= 4.0.13)
+      activerecord (= 4.0.13)
+      activesupport (= 4.0.13)
+      bundler (>= 1.3.0, < 2.0)
+      railties (= 4.0.13)
+      sprockets-rails (~> 2.0)
+    railties (4.0.13)
+      actionpack (= 4.0.13)
+      activesupport (= 4.0.13)
+      rake (>= 0.8.7)
+      thor (>= 0.18.1, < 2.0)
+    rake (12.3.3)
+    rspec (3.9.0)
+      rspec-core (~> 3.9.0)
+      rspec-expectations (~> 3.9.0)
+      rspec-mocks (~> 3.9.0)
+    rspec-core (3.9.0)
+      rspec-support (~> 3.9.0)
+    rspec-expectations (3.9.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.9.0)
+    rspec-mocks (3.9.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.9.0)
+    rspec-support (3.9.0)
+    simplecov (0.16.1)
+      docile (~> 1.1)
+      json (>= 1.8, < 3)
+      simplecov-html (~> 0.10.0)
+    simplecov-html (0.10.2)
+    sprockets (3.7.2)
+      concurrent-ruby (~> 1.0)
+      rack (> 1, < 3)
+    sprockets-rails (2.3.3)
+      actionpack (>= 3.0)
+      activesupport (>= 3.0)
+      sprockets (>= 2.8, < 4.0)
+    sqlite3 (1.3.13)
+    term-ansicolor (1.7.1)
+      tins (~> 1.0)
+    thor (0.20.3)
+    thread_safe (0.3.6)
+    tins (1.21.1)
+    tzinfo (0.3.55)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  appraisal
+  bundler (~> 1.17)
+  coveralls
+  rails (~> 4.0.0)
+  rake (~> 12.0)
+  rspec
+  sqlite3 (~> 1.3, < 1.4)
+  uniqueness!
+
+BUNDLED WITH
+   1.17.3
diff --git a/gemfiles/41.gemfile b/gemfiles/41.gemfile
new file mode 100644
index 0000000..f4a887f
--- /dev/null
+++ b/gemfiles/41.gemfile
@@ -0,0 +1,7 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rails", "~> 4.1.0"
+
+gemspec path: "../"
diff --git a/gemfiles/41.gemfile.lock b/gemfiles/41.gemfile.lock
new file mode 100644
index 0000000..fea5a70
--- /dev/null
+++ b/gemfiles/41.gemfile.lock
@@ -0,0 +1,127 @@
+PATH
+  remote: ..
+  specs:
+    uniqueness (1.1.1)
+      activerecord (>= 4.0.0)
+      railties (>= 4.0.0)
+
+GEM
+  remote: https://rubygems.org/
+  specs:
+    actionmailer (4.1.16)
+      actionpack (= 4.1.16)
+      actionview (= 4.1.16)
+      mail (~> 2.5, >= 2.5.4)
+    actionpack (4.1.16)
+      actionview (= 4.1.16)
+      activesupport (= 4.1.16)
+      rack (~> 1.5.2)
+      rack-test (~> 0.6.2)
+    actionview (4.1.16)
+      activesupport (= 4.1.16)
+      builder (~> 3.1)
+      erubis (~> 2.7.0)
+    activemodel (4.1.16)
+      activesupport (= 4.1.16)
+      builder (~> 3.1)
+    activerecord (4.1.16)
+      activemodel (= 4.1.16)
+      activesupport (= 4.1.16)
+      arel (~> 5.0.0)
+    activesupport (4.1.16)
+      i18n (~> 0.6, >= 0.6.9)
+      json (~> 1.7, >= 1.7.7)
+      minitest (~> 5.1)
+      thread_safe (~> 0.1)
+      tzinfo (~> 1.1)
+    appraisal (2.2.0)
+      bundler
+      rake
+      thor (>= 0.14.0)
+    arel (5.0.1.20140414130214)
+    builder (3.2.3)
+    concurrent-ruby (1.1.5)
+    coveralls (0.8.23)
+      json (>= 1.8, < 3)
+      simplecov (~> 0.16.1)
+      term-ansicolor (~> 1.3)
+      thor (>= 0.19.4, < 2.0)
+      tins (~> 1.6)
+    diff-lcs (1.3)
+    docile (1.3.2)
+    erubis (2.7.0)
+    i18n (0.9.5)
+      concurrent-ruby (~> 1.0)
+    json (1.8.6)
+    mail (2.7.1)
+      mini_mime (>= 0.1.1)
+    mini_mime (1.0.2)
+    minitest (5.12.2)
+    rack (1.5.5)
+    rack-test (0.6.3)
+      rack (>= 1.0)
+    rails (4.1.16)
+      actionmailer (= 4.1.16)
+      actionpack (= 4.1.16)
+      actionview (= 4.1.16)
+      activemodel (= 4.1.16)
+      activerecord (= 4.1.16)
+      activesupport (= 4.1.16)
+      bundler (>= 1.3.0, < 2.0)
+      railties (= 4.1.16)
+      sprockets-rails (~> 2.0)
+    railties (4.1.16)
+      actionpack (= 4.1.16)
+      activesupport (= 4.1.16)
+      rake (>= 0.8.7)
+      thor (>= 0.18.1, < 2.0)
+    rake (12.3.3)
+    rspec (3.9.0)
+      rspec-core (~> 3.9.0)
+      rspec-expectations (~> 3.9.0)
+      rspec-mocks (~> 3.9.0)
+    rspec-core (3.9.0)
+      rspec-support (~> 3.9.0)
+    rspec-expectations (3.9.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.9.0)
+    rspec-mocks (3.9.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.9.0)
+    rspec-support (3.9.0)
+    simplecov (0.16.1)
+      docile (~> 1.1)
+      json (>= 1.8, < 3)
+      simplecov-html (~> 0.10.0)
+    simplecov-html (0.10.2)
+    sprockets (3.7.2)
+      concurrent-ruby (~> 1.0)
+      rack (> 1, < 3)
+    sprockets-rails (2.3.3)
+      actionpack (>= 3.0)
+      activesupport (>= 3.0)
+      sprockets (>= 2.8, < 4.0)
+    sqlite3 (1.3.13)
+    term-ansicolor (1.7.1)
+      tins (~> 1.0)
+    thor (0.20.3)
+    thread_safe (0.3.6)
+    tins (1.21.1)
+    tzinfo (1.2.5)
+      thread_safe (~> 0.1)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  appraisal
+  bundler (~> 1.17)
+  coveralls
+  rails (~> 4.1.0)
+  rake (~> 12.0)
+  rspec
+  sqlite3 (~> 1.3, < 1.4)
+  uniqueness!
+
+BUNDLED WITH
+   1.17.3
diff --git a/gemfiles/42.gemfile b/gemfiles/42.gemfile
new file mode 100644
index 0000000..6977eb0
--- /dev/null
+++ b/gemfiles/42.gemfile
@@ -0,0 +1,7 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rails", "~> 4.2.0"
+
+gemspec path: "../"
diff --git a/gemfiles/42.gemfile.lock b/gemfiles/42.gemfile.lock
new file mode 100644
index 0000000..d44fa01
--- /dev/null
+++ b/gemfiles/42.gemfile.lock
@@ -0,0 +1,153 @@
+PATH
+  remote: ..
+  specs:
+    uniqueness (1.1.1)
+      activerecord (>= 4.0.0)
+      railties (>= 4.0.0)
+
+GEM
+  remote: https://rubygems.org/
+  specs:
+    actionmailer (4.2.11.1)
+      actionpack (= 4.2.11.1)
+      actionview (= 4.2.11.1)
+      activejob (= 4.2.11.1)
+      mail (~> 2.5, >= 2.5.4)
+      rails-dom-testing (~> 1.0, >= 1.0.5)
+    actionpack (4.2.11.1)
+      actionview (= 4.2.11.1)
+      activesupport (= 4.2.11.1)
+      rack (~> 1.6)
+      rack-test (~> 0.6.2)
+      rails-dom-testing (~> 1.0, >= 1.0.5)
+      rails-html-sanitizer (~> 1.0, >= 1.0.2)
+    actionview (4.2.11.1)
+      activesupport (= 4.2.11.1)
+      builder (~> 3.1)
+      erubis (~> 2.7.0)
+      rails-dom-testing (~> 1.0, >= 1.0.5)
+      rails-html-sanitizer (~> 1.0, >= 1.0.3)
+    activejob (4.2.11.1)
+      activesupport (= 4.2.11.1)
+      globalid (>= 0.3.0)
+    activemodel (4.2.11.1)
+      activesupport (= 4.2.11.1)
+      builder (~> 3.1)
+    activerecord (4.2.11.1)
+      activemodel (= 4.2.11.1)
+      activesupport (= 4.2.11.1)
+      arel (~> 6.0)
+    activesupport (4.2.11.1)
+      i18n (~> 0.7)
+      minitest (~> 5.1)
+      thread_safe (~> 0.3, >= 0.3.4)
+      tzinfo (~> 1.1)
+    appraisal (2.2.0)
+      bundler
+      rake
+      thor (>= 0.14.0)
+    arel (6.0.4)
+    builder (3.2.3)
+    concurrent-ruby (1.1.5)
+    coveralls (0.8.23)
+      json (>= 1.8, < 3)
+      simplecov (~> 0.16.1)
+      term-ansicolor (~> 1.3)
+      thor (>= 0.19.4, < 2.0)
+      tins (~> 1.6)
+    crass (1.0.5)
+    diff-lcs (1.3)
+    docile (1.3.2)
+    erubis (2.7.0)
+    globalid (0.4.2)
+      activesupport (>= 4.2.0)
+    i18n (0.9.5)
+      concurrent-ruby (~> 1.0)
+    json (2.2.0)
+    loofah (2.3.1)
+      crass (~> 1.0.2)
+      nokogiri (>= 1.5.9)
+    mail (2.7.1)
+      mini_mime (>= 0.1.1)
+    mini_mime (1.0.2)
+    mini_portile2 (2.4.0)
+    minitest (5.12.2)
+    nokogiri (1.10.4)
+      mini_portile2 (~> 2.4.0)
+    rack (1.6.11)
+    rack-test (0.6.3)
+      rack (>= 1.0)
+    rails (4.2.11.1)
+      actionmailer (= 4.2.11.1)
+      actionpack (= 4.2.11.1)
+      actionview (= 4.2.11.1)
+      activejob (= 4.2.11.1)
+      activemodel (= 4.2.11.1)
+      activerecord (= 4.2.11.1)
+      activesupport (= 4.2.11.1)
+      bundler (>= 1.3.0, < 2.0)
+      railties (= 4.2.11.1)
+      sprockets-rails
+    rails-deprecated_sanitizer (1.0.3)
+      activesupport (>= 4.2.0.alpha)
+    rails-dom-testing (1.0.9)
+      activesupport (>= 4.2.0, < 5.0)
+      nokogiri (~> 1.6)
+      rails-deprecated_sanitizer (>= 1.0.1)
+    rails-html-sanitizer (1.3.0)
+      loofah (~> 2.3)
+    railties (4.2.11.1)
+      actionpack (= 4.2.11.1)
+      activesupport (= 4.2.11.1)
+      rake (>= 0.8.7)
+      thor (>= 0.18.1, < 2.0)
+    rake (12.3.3)
+    rspec (3.9.0)
+      rspec-core (~> 3.9.0)
+      rspec-expectations (~> 3.9.0)
+      rspec-mocks (~> 3.9.0)
+    rspec-core (3.9.0)
+      rspec-support (~> 3.9.0)
+    rspec-expectations (3.9.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.9.0)
+    rspec-mocks (3.9.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.9.0)
+    rspec-support (3.9.0)
+    simplecov (0.16.1)
+      docile (~> 1.1)
+      json (>= 1.8, < 3)
+      simplecov-html (~> 0.10.0)
+    simplecov-html (0.10.2)
+    sprockets (4.0.0)
+      concurrent-ruby (~> 1.0)
+      rack (> 1, < 3)
+    sprockets-rails (3.2.1)
+      actionpack (>= 4.0)
+      activesupport (>= 4.0)
+      sprockets (>= 3.0.0)
+    sqlite3 (1.3.13)
+    term-ansicolor (1.7.1)
+      tins (~> 1.0)
+    thor (0.20.3)
+    thread_safe (0.3.6)
+    tins (1.21.1)
+    tzinfo (1.2.5)
+      thread_safe (~> 0.1)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  appraisal
+  bundler (~> 1.17)
+  coveralls
+  rails (~> 4.2.0)
+  rake (~> 12.0)
+  rspec
+  sqlite3 (~> 1.3, < 1.4)
+  uniqueness!
+
+BUNDLED WITH
+   1.17.3
diff --git a/gemfiles/5.0.gemfile b/gemfiles/5.0.gemfile
index 6b40de0..10f52e7 100644
--- a/gemfiles/5.0.gemfile
+++ b/gemfiles/5.0.gemfile
@@ -2,7 +2,6 @@
 
 source "https://rubygems.org"
 
-gem "bundler", "~> 2.0"
 gem "rails", "~> 5.0.0"
 
 gemspec path: "../"
diff --git a/gemfiles/5.0.gemfile.lock b/gemfiles/5.0.gemfile.lock
index dc49fbf..430ec9a 100644
--- a/gemfiles/5.0.gemfile.lock
+++ b/gemfiles/5.0.gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: ..
   specs:
-    uniqueness (1.1.0)
+    uniqueness (1.1.1)
       activerecord (>= 4.0.0)
       railties (>= 4.0.0)
 
@@ -52,32 +52,32 @@ GEM
     arel (7.1.4)
     builder (3.2.3)
     concurrent-ruby (1.1.5)
-    coveralls (0.8.22)
+    coveralls (0.8.23)
       json (>= 1.8, < 3)
       simplecov (~> 0.16.1)
       term-ansicolor (~> 1.3)
-      thor (~> 0.19.4)
+      thor (>= 0.19.4, < 2.0)
       tins (~> 1.6)
-    crass (1.0.4)
+    crass (1.0.5)
     diff-lcs (1.3)
-    docile (1.3.1)
+    docile (1.3.2)
     erubis (2.7.0)
     globalid (0.4.2)
       activesupport (>= 4.2.0)
-    i18n (1.6.0)
+    i18n (1.7.0)
       concurrent-ruby (~> 1.0)
     json (2.2.0)
-    loofah (2.2.3)
+    loofah (2.3.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)
       mini_mime (>= 0.1.1)
     method_source (0.9.2)
-    mini_mime (1.0.1)
+    mini_mime (1.0.2)
     mini_portile2 (2.4.0)
-    minitest (5.11.3)
-    nio4r (2.3.1)
-    nokogiri (1.10.2)
+    minitest (5.12.2)
+    nio4r (2.5.2)
+    nokogiri (1.10.4)
       mini_portile2 (~> 2.4.0)
     rack (2.0.7)
     rack-test (0.6.3)
@@ -97,34 +97,34 @@ GEM
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.0.4)
-      loofah (~> 2.2, >= 2.2.2)
+    rails-html-sanitizer (1.3.0)
+      loofah (~> 2.3)
     railties (5.0.7.2)
       actionpack (= 5.0.7.2)
       activesupport (= 5.0.7.2)
       method_source
       rake (>= 0.8.7)
       thor (>= 0.18.1, < 2.0)
-    rake (12.3.2)
-    rspec (3.8.0)
-      rspec-core (~> 3.8.0)
-      rspec-expectations (~> 3.8.0)
-      rspec-mocks (~> 3.8.0)
-    rspec-core (3.8.0)
-      rspec-support (~> 3.8.0)
-    rspec-expectations (3.8.2)
+    rake (12.3.3)
+    rspec (3.9.0)
+      rspec-core (~> 3.9.0)
+      rspec-expectations (~> 3.9.0)
+      rspec-mocks (~> 3.9.0)
+    rspec-core (3.9.0)
+      rspec-support (~> 3.9.0)
+    rspec-expectations (3.9.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-mocks (3.8.0)
+      rspec-support (~> 3.9.0)
+    rspec-mocks (3.9.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-support (3.8.0)
+      rspec-support (~> 3.9.0)
+    rspec-support (3.9.0)
     simplecov (0.16.1)
       docile (~> 1.1)
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    sprockets (3.7.2)
+    sprockets (4.0.0)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     sprockets-rails (3.2.1)
@@ -134,21 +134,21 @@ GEM
     sqlite3 (1.3.13)
     term-ansicolor (1.7.1)
       tins (~> 1.0)
-    thor (0.19.4)
+    thor (0.20.3)
     thread_safe (0.3.6)
-    tins (1.20.2)
+    tins (1.21.1)
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
     websocket-driver (0.6.5)
       websocket-extensions (>= 0.1.0)
-    websocket-extensions (0.1.3)
+    websocket-extensions (0.1.4)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
   appraisal
-  bundler (~> 2.0)
+  bundler (~> 1.17)
   coveralls
   rails (~> 5.0.0)
   rake (~> 12.0)
@@ -157,4 +157,4 @@ DEPENDENCIES
   uniqueness!
 
 BUNDLED WITH
-   2.0.1
+   1.17.3
diff --git a/gemfiles/5.1.gemfile b/gemfiles/5.1.gemfile
index 599e01b..6100e83 100644
--- a/gemfiles/5.1.gemfile
+++ b/gemfiles/5.1.gemfile
@@ -2,7 +2,6 @@
 
 source "https://rubygems.org"
 
-gem "bundler", "~> 2.0"
 gem "rails", "~> 5.1.0"
 
 gemspec path: "../"
diff --git a/gemfiles/5.1.gemfile.lock b/gemfiles/5.1.gemfile.lock
index 4beaee1..6bf6cd7 100644
--- a/gemfiles/5.1.gemfile.lock
+++ b/gemfiles/5.1.gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: ..
   specs:
-    uniqueness (1.1.0)
+    uniqueness (1.1.1)
       activerecord (>= 4.0.0)
       railties (>= 4.0.0)
 
@@ -52,32 +52,32 @@ GEM
     arel (8.0.0)
     builder (3.2.3)
     concurrent-ruby (1.1.5)
-    coveralls (0.8.22)
+    coveralls (0.8.23)
       json (>= 1.8, < 3)
       simplecov (~> 0.16.1)
       term-ansicolor (~> 1.3)
-      thor (~> 0.19.4)
+      thor (>= 0.19.4, < 2.0)
       tins (~> 1.6)
-    crass (1.0.4)
+    crass (1.0.5)
     diff-lcs (1.3)
-    docile (1.3.1)
-    erubi (1.8.0)
+    docile (1.3.2)
+    erubi (1.9.0)
     globalid (0.4.2)
       activesupport (>= 4.2.0)
-    i18n (1.6.0)
+    i18n (1.7.0)
       concurrent-ruby (~> 1.0)
     json (2.2.0)
-    loofah (2.2.3)
+    loofah (2.3.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)
       mini_mime (>= 0.1.1)
     method_source (0.9.2)
-    mini_mime (1.0.1)
+    mini_mime (1.0.2)
     mini_portile2 (2.4.0)
-    minitest (5.11.3)
-    nio4r (2.3.1)
-    nokogiri (1.10.2)
+    minitest (5.12.2)
+    nio4r (2.5.2)
+    nokogiri (1.10.4)
       mini_portile2 (~> 2.4.0)
     rack (2.0.7)
     rack-test (1.1.0)
@@ -97,34 +97,34 @@ GEM
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.0.4)
-      loofah (~> 2.2, >= 2.2.2)
+    rails-html-sanitizer (1.3.0)
+      loofah (~> 2.3)
     railties (5.1.7)
       actionpack (= 5.1.7)
       activesupport (= 5.1.7)
       method_source
       rake (>= 0.8.7)
       thor (>= 0.18.1, < 2.0)
-    rake (12.3.2)
-    rspec (3.8.0)
-      rspec-core (~> 3.8.0)
-      rspec-expectations (~> 3.8.0)
-      rspec-mocks (~> 3.8.0)
-    rspec-core (3.8.0)
-      rspec-support (~> 3.8.0)
-    rspec-expectations (3.8.2)
+    rake (12.3.3)
+    rspec (3.9.0)
+      rspec-core (~> 3.9.0)
+      rspec-expectations (~> 3.9.0)
+      rspec-mocks (~> 3.9.0)
+    rspec-core (3.9.0)
+      rspec-support (~> 3.9.0)
+    rspec-expectations (3.9.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-mocks (3.8.0)
+      rspec-support (~> 3.9.0)
+    rspec-mocks (3.9.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-support (3.8.0)
+      rspec-support (~> 3.9.0)
+    rspec-support (3.9.0)
     simplecov (0.16.1)
       docile (~> 1.1)
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    sprockets (3.7.2)
+    sprockets (4.0.0)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     sprockets-rails (3.2.1)
@@ -134,21 +134,21 @@ GEM
     sqlite3 (1.3.13)
     term-ansicolor (1.7.1)
       tins (~> 1.0)
-    thor (0.19.4)
+    thor (0.20.3)
     thread_safe (0.3.6)
-    tins (1.20.2)
+    tins (1.21.1)
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
     websocket-driver (0.6.5)
       websocket-extensions (>= 0.1.0)
-    websocket-extensions (0.1.3)
+    websocket-extensions (0.1.4)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
   appraisal
-  bundler (~> 2.0)
+  bundler (~> 1.17)
   coveralls
   rails (~> 5.1.0)
   rake (~> 12.0)
@@ -157,4 +157,4 @@ DEPENDENCIES
   uniqueness!
 
 BUNDLED WITH
-   2.0.1
+   1.17.3
diff --git a/gemfiles/5.2.gemfile b/gemfiles/5.2.gemfile
index 31f3118..5a706dc 100644
--- a/gemfiles/5.2.gemfile
+++ b/gemfiles/5.2.gemfile
@@ -2,7 +2,6 @@
 
 source "https://rubygems.org"
 
-gem "bundler", "~> 2.0"
 gem "rails", "~> 5.2.0"
 
 gemspec path: "../"
diff --git a/gemfiles/5.2.gemfile.lock b/gemfiles/5.2.gemfile.lock
index ffcfe31..8545e04 100644
--- a/gemfiles/5.2.gemfile.lock
+++ b/gemfiles/5.2.gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: ..
   specs:
-    uniqueness (1.1.0)
+    uniqueness (1.1.1)
       activerecord (>= 4.0.0)
       railties (>= 4.0.0)
 
@@ -56,22 +56,22 @@ GEM
     arel (9.0.0)
     builder (3.2.3)
     concurrent-ruby (1.1.5)
-    coveralls (0.8.22)
+    coveralls (0.8.23)
       json (>= 1.8, < 3)
       simplecov (~> 0.16.1)
       term-ansicolor (~> 1.3)
-      thor (~> 0.19.4)
+      thor (>= 0.19.4, < 2.0)
       tins (~> 1.6)
-    crass (1.0.4)
+    crass (1.0.5)
     diff-lcs (1.3)
-    docile (1.3.1)
-    erubi (1.8.0)
+    docile (1.3.2)
+    erubi (1.9.0)
     globalid (0.4.2)
       activesupport (>= 4.2.0)
-    i18n (1.6.0)
+    i18n (1.7.0)
       concurrent-ruby (~> 1.0)
     json (2.2.0)
-    loofah (2.2.3)
+    loofah (2.3.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)
@@ -80,11 +80,11 @@ GEM
       mimemagic (~> 0.3.2)
     method_source (0.9.2)
     mimemagic (0.3.3)
-    mini_mime (1.0.1)
+    mini_mime (1.0.2)
     mini_portile2 (2.4.0)
-    minitest (5.11.3)
-    nio4r (2.3.1)
-    nokogiri (1.10.2)
+    minitest (5.12.2)
+    nio4r (2.5.2)
+    nokogiri (1.10.4)
       mini_portile2 (~> 2.4.0)
     rack (2.0.7)
     rack-test (1.1.0)
@@ -105,34 +105,34 @@ GEM
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.0.4)
-      loofah (~> 2.2, >= 2.2.2)
+    rails-html-sanitizer (1.3.0)
+      loofah (~> 2.3)
     railties (5.2.3)
       actionpack (= 5.2.3)
       activesupport (= 5.2.3)
       method_source
       rake (>= 0.8.7)
       thor (>= 0.19.0, < 2.0)
-    rake (12.3.2)
-    rspec (3.8.0)
-      rspec-core (~> 3.8.0)
-      rspec-expectations (~> 3.8.0)
-      rspec-mocks (~> 3.8.0)
-    rspec-core (3.8.0)
-      rspec-support (~> 3.8.0)
-    rspec-expectations (3.8.2)
+    rake (12.3.3)
+    rspec (3.9.0)
+      rspec-core (~> 3.9.0)
+      rspec-expectations (~> 3.9.0)
+      rspec-mocks (~> 3.9.0)
+    rspec-core (3.9.0)
+      rspec-support (~> 3.9.0)
+    rspec-expectations (3.9.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-mocks (3.8.0)
+      rspec-support (~> 3.9.0)
+    rspec-mocks (3.9.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-support (3.8.0)
+      rspec-support (~> 3.9.0)
+    rspec-support (3.9.0)
     simplecov (0.16.1)
       docile (~> 1.1)
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    sprockets (3.7.2)
+    sprockets (4.0.0)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     sprockets-rails (3.2.1)
@@ -142,21 +142,21 @@ GEM
     sqlite3 (1.3.13)
     term-ansicolor (1.7.1)
       tins (~> 1.0)
-    thor (0.19.4)
+    thor (0.20.3)
     thread_safe (0.3.6)
-    tins (1.20.2)
+    tins (1.21.1)
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
-    websocket-driver (0.7.0)
+    websocket-driver (0.7.1)
       websocket-extensions (>= 0.1.0)
-    websocket-extensions (0.1.3)
+    websocket-extensions (0.1.4)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
   appraisal
-  bundler (~> 2.0)
+  bundler (~> 1.17)
   coveralls
   rails (~> 5.2.0)
   rake (~> 12.0)
@@ -165,4 +165,4 @@ DEPENDENCIES
   uniqueness!
 
 BUNDLED WITH
-   2.0.1
+   1.17.3
diff --git a/gemfiles/6.0.gemfile b/gemfiles/6.0.gemfile
index bbbbe97..15b9b27 100644
--- a/gemfiles/6.0.gemfile
+++ b/gemfiles/6.0.gemfile
@@ -2,7 +2,6 @@
 
 source "https://rubygems.org"
 
-gem "bundler", "~> 2.0"
-gem "rails", "6.0.0.beta3"
+gem "rails", "~> 6.0.0"
 
 gemspec path: "../"
diff --git a/gemfiles/6.0.gemfile.lock b/gemfiles/6.0.gemfile.lock
index 83472bf..5cdd232 100644
--- a/gemfiles/6.0.gemfile.lock
+++ b/gemfiles/6.0.gemfile.lock
@@ -1,93 +1,90 @@
 PATH
   remote: ..
   specs:
-    uniqueness (1.1.0)
+    uniqueness (1.1.1)
       activerecord (>= 4.0.0)
       railties (>= 4.0.0)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    actioncable (6.0.0.beta3)
-      actionpack (= 6.0.0.beta3)
+    actioncable (6.0.0)
+      actionpack (= 6.0.0)
       nio4r (~> 2.0)
       websocket-driver (>= 0.6.1)
-    actionmailbox (6.0.0.beta3)
-      actionpack (= 6.0.0.beta3)
-      activejob (= 6.0.0.beta3)
-      activerecord (= 6.0.0.beta3)
-      activestorage (= 6.0.0.beta3)
-      activesupport (= 6.0.0.beta3)
+    actionmailbox (6.0.0)
+      actionpack (= 6.0.0)
+      activejob (= 6.0.0)
+      activerecord (= 6.0.0)
+      activestorage (= 6.0.0)
+      activesupport (= 6.0.0)
       mail (>= 2.7.1)
-    actionmailer (6.0.0.beta3)
-      actionpack (= 6.0.0.beta3)
-      actionview (= 6.0.0.beta3)
-      activejob (= 6.0.0.beta3)
+    actionmailer (6.0.0)
+      actionpack (= 6.0.0)
+      actionview (= 6.0.0)
+      activejob (= 6.0.0)
       mail (~> 2.5, >= 2.5.4)
       rails-dom-testing (~> 2.0)
-    actionpack (6.0.0.beta3)
-      actionview (= 6.0.0.beta3)
-      activesupport (= 6.0.0.beta3)
+    actionpack (6.0.0)
+      actionview (= 6.0.0)
+      activesupport (= 6.0.0)
       rack (~> 2.0)
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.0)
-      rails-html-sanitizer (~> 1.0, >= 1.0.2)
-    actiontext (6.0.0.beta3)
-      actionpack (= 6.0.0.beta3)
-      activerecord (= 6.0.0.beta3)
-      activestorage (= 6.0.0.beta3)
-      activesupport (= 6.0.0.beta3)
+      rails-html-sanitizer (~> 1.0, >= 1.2.0)
+    actiontext (6.0.0)
+      actionpack (= 6.0.0)
+      activerecord (= 6.0.0)
+      activestorage (= 6.0.0)
+      activesupport (= 6.0.0)
       nokogiri (>= 1.8.5)
-    actionview (6.0.0.beta3)
-      activesupport (= 6.0.0.beta3)
+    actionview (6.0.0)
+      activesupport (= 6.0.0)
       builder (~> 3.1)
       erubi (~> 1.4)
       rails-dom-testing (~> 2.0)
-      rails-html-sanitizer (~> 1.0, >= 1.0.3)
-    activejob (6.0.0.beta3)
-      activesupport (= 6.0.0.beta3)
+      rails-html-sanitizer (~> 1.1, >= 1.2.0)
+    activejob (6.0.0)
+      activesupport (= 6.0.0)
       globalid (>= 0.3.6)
-    activemodel (6.0.0.beta3)
-      activesupport (= 6.0.0.beta3)
-    activerecord (6.0.0.beta3)
-      activemodel (= 6.0.0.beta3)
-      activesupport (= 6.0.0.beta3)
-    activestorage (6.0.0.beta3)
-      actionpack (= 6.0.0.beta3)
-      activerecord (= 6.0.0.beta3)
+    activemodel (6.0.0)
+      activesupport (= 6.0.0)
+    activerecord (6.0.0)
+      activemodel (= 6.0.0)
+      activesupport (= 6.0.0)
+    activestorage (6.0.0)
+      actionpack (= 6.0.0)
+      activejob (= 6.0.0)
+      activerecord (= 6.0.0)
       marcel (~> 0.3.1)
-    activesupport (6.0.0.beta3)
+    activesupport (6.0.0)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-      zeitwerk (~> 1.3, >= 1.3.1)
+      zeitwerk (~> 2.1, >= 2.1.8)
     appraisal (2.2.0)
       bundler
       rake
       thor (>= 0.14.0)
     builder (3.2.3)
     concurrent-ruby (1.1.5)
-    coveralls (0.7.1)
-      multi_json (~> 1.3)
-      rest-client
-      simplecov (>= 0.7)
-      term-ansicolor
-      thor
-    crass (1.0.4)
+    coveralls (0.8.23)
+      json (>= 1.8, < 3)
+      simplecov (~> 0.16.1)
+      term-ansicolor (~> 1.3)
+      thor (>= 0.19.4, < 2.0)
+      tins (~> 1.6)
+    crass (1.0.5)
     diff-lcs (1.3)
-    docile (1.3.1)
-    domain_name (0.5.20180417)
-      unf (>= 0.0.5, < 1.0.0)
-    erubi (1.8.0)
+    docile (1.3.2)
+    erubi (1.9.0)
     globalid (0.4.2)
       activesupport (>= 4.2.0)
-    http-cookie (1.0.3)
-      domain_name (~> 0.5)
-    i18n (1.6.0)
+    i18n (1.7.0)
       concurrent-ruby (~> 1.0)
     json (2.2.0)
-    loofah (2.2.3)
+    loofah (2.3.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)
@@ -95,71 +92,62 @@ GEM
     marcel (0.3.3)
       mimemagic (~> 0.3.2)
     method_source (0.9.2)
-    mime-types (3.2.2)
-      mime-types-data (~> 3.2015)
-    mime-types-data (3.2019.0331)
     mimemagic (0.3.3)
-    mini_mime (1.0.1)
+    mini_mime (1.0.2)
     mini_portile2 (2.4.0)
-    minitest (5.11.3)
-    multi_json (1.13.1)
-    netrc (0.11.0)
-    nio4r (2.3.1)
-    nokogiri (1.10.2)
+    minitest (5.12.2)
+    nio4r (2.5.2)
+    nokogiri (1.10.4)
       mini_portile2 (~> 2.4.0)
     rack (2.0.7)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
-    rails (6.0.0.beta3)
-      actioncable (= 6.0.0.beta3)
-      actionmailbox (= 6.0.0.beta3)
-      actionmailer (= 6.0.0.beta3)
-      actionpack (= 6.0.0.beta3)
-      actiontext (= 6.0.0.beta3)
-      actionview (= 6.0.0.beta3)
-      activejob (= 6.0.0.beta3)
-      activemodel (= 6.0.0.beta3)
-      activerecord (= 6.0.0.beta3)
-      activestorage (= 6.0.0.beta3)
-      activesupport (= 6.0.0.beta3)
+    rails (6.0.0)
+      actioncable (= 6.0.0)
+      actionmailbox (= 6.0.0)
+      actionmailer (= 6.0.0)
+      actionpack (= 6.0.0)
+      actiontext (= 6.0.0)
+      actionview (= 6.0.0)
+      activejob (= 6.0.0)
+      activemodel (= 6.0.0)
+      activerecord (= 6.0.0)
+      activestorage (= 6.0.0)
+      activesupport (= 6.0.0)
       bundler (>= 1.3.0)
-      railties (= 6.0.0.beta3)
+      railties (= 6.0.0)
       sprockets-rails (>= 2.0.0)
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.0.4)
-      loofah (~> 2.2, >= 2.2.2)
-    railties (6.0.0.beta3)
-      actionpack (= 6.0.0.beta3)
-      activesupport (= 6.0.0.beta3)
+    rails-html-sanitizer (1.3.0)
+      loofah (~> 2.3)
+    railties (6.0.0)
+      actionpack (= 6.0.0)
+      activesupport (= 6.0.0)
       method_source
       rake (>= 0.8.7)
       thor (>= 0.20.3, < 2.0)
-    rake (12.3.2)
-    rest-client (2.0.2)
-      http-cookie (>= 1.0.2, < 2.0)
-      mime-types (>= 1.16, < 4.0)
-      netrc (~> 0.8)
-    rspec (3.8.0)
-      rspec-core (~> 3.8.0)
-      rspec-expectations (~> 3.8.0)
-      rspec-mocks (~> 3.8.0)
-    rspec-core (3.8.0)
-      rspec-support (~> 3.8.0)
-    rspec-expectations (3.8.2)
+    rake (12.3.3)
+    rspec (3.9.0)
+      rspec-core (~> 3.9.0)
+      rspec-expectations (~> 3.9.0)
+      rspec-mocks (~> 3.9.0)
+    rspec-core (3.9.0)
+      rspec-support (~> 3.9.0)
+    rspec-expectations (3.9.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-mocks (3.8.0)
+      rspec-support (~> 3.9.0)
+    rspec-mocks (3.9.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-support (3.8.0)
+      rspec-support (~> 3.9.0)
+    rspec-support (3.9.0)
     simplecov (0.16.1)
       docile (~> 1.1)
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    sprockets (3.7.2)
+    sprockets (4.0.0)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     sprockets-rails (3.2.1)
@@ -171,29 +159,26 @@ GEM
       tins (~> 1.0)
     thor (0.20.3)
     thread_safe (0.3.6)
-    tins (1.20.2)
+    tins (1.21.1)
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
-    unf (0.1.4)
-      unf_ext
-    unf_ext (0.0.7.5)
-    websocket-driver (0.7.0)
+    websocket-driver (0.7.1)
       websocket-extensions (>= 0.1.0)
-    websocket-extensions (0.1.3)
-    zeitwerk (1.4.3)
+    websocket-extensions (0.1.4)
+    zeitwerk (2.2.0)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
   appraisal
-  bundler (~> 2.0)
+  bundler (~> 1.17)
   coveralls
-  rails (= 6.0.0.beta3)
+  rails (~> 6.0.0)
   rake (~> 12.0)
   rspec
   sqlite3 (~> 1.3, < 1.4)
   uniqueness!
 
 BUNDLED WITH
-   2.0.1
+   1.17.3
diff --git a/lib/uniqueness/generator.rb b/lib/uniqueness/generator.rb
index e70421e..6091c35 100644
--- a/lib/uniqueness/generator.rb
+++ b/lib/uniqueness/generator.rb
@@ -3,12 +3,12 @@
 module Uniqueness
   class << self
     def generate(opts = {})
-      options ||= {}
       options = uniqueness_default_options.merge(opts)
       dict = uniqueness_dictionary - options[:blacklist]
       dict -= [*(:A..:Z)].map(&:to_s) unless options[:case_sensitive]
       dict -= uniqueness_ambigious_dictionary if options[:type].to_sym == :human
       dict = uniqueness_numbers_dictionary if options[:type].to_sym == :numbers
+      dict = uniqueness_custom_dictionary(options[:chars]) if options[:chars].present?
       code = Array.new(options[:length]).map { dict[SecureRandom.random_number(dict.length)] }.join
       "#{options[:prefix]}#{code}#{options[:suffix]}"
     end
@@ -26,6 +26,12 @@ def uniqueness_numbers_dictionary
       [*(0..9)].map(&:to_s)
     end
 
+    def uniqueness_custom_dictionary(chars = [])
+      chars = [*chars] if chars.is_a?(Range)
+      chars = chars.map(&:to_s) if chars.is_a?(Array)
+      chars
+    end
+
     # Default sorting options
     def uniqueness_default_options
       {
diff --git a/lib/uniqueness/model.rb b/lib/uniqueness/model.rb
index e89e507..9d6a7df 100644
--- a/lib/uniqueness/model.rb
+++ b/lib/uniqueness/model.rb
@@ -46,17 +46,21 @@ def has_unique_field(name, options = {})
         end
 
         validate :uniqueness_validation
-        define_method("regenerate_#{name}") { update(name => Uniqueness.generate(self.uniqueness_options[name])) }
+
+        define_method("regenerate_#{name}") do
+          value = Uniqueness.generate(uniqueness_options[name])
+          send("#{name}=", value)
+        end
       end
     end
 
     # Generates a new code based on given options
     def uniqueness_generate
-      self.uniqueness_options.each do |field, options|
+      uniqueness_options.each do |field, options|
         value = send(field)
         unless value.present?
           value = Uniqueness.generate(options)
-          self.send("#{field}=", value)
+          send("#{field}=", value)
         end
       end
     end
diff --git a/lib/uniqueness/version.rb b/lib/uniqueness/version.rb
index d8025c9..ff4ef0e 100644
--- a/lib/uniqueness/version.rb
+++ b/lib/uniqueness/version.rb
@@ -1,3 +1,3 @@
 module Uniqueness
-  VERSION = '1.1.0'.freeze
+  VERSION = '1.1.1'.freeze
 end
diff --git a/spec/generator/generator_spec.rb b/spec/generator/generator_spec.rb
index 6386233..31bc1e2 100644
--- a/spec/generator/generator_spec.rb
+++ b/spec/generator/generator_spec.rb
@@ -6,5 +6,8 @@
     it { expect(Uniqueness.generate(type: :numbers)).to match(/^[0-9]+$/) }
     it { expect(Uniqueness.generate(prefix: 'hassan').index('hassan')).to eq 0 }
     it { expect(Uniqueness.generate(suffix: 'hassan')).to end_with "hassan" }
+    it { expect(Uniqueness.generate(chars: 'A'..'F')).to match(/^[A-F]+$/) }
+    it { expect(Uniqueness.generate(chars: ('A'..'F').to_a)).to match(/^[A-F]+$/) }
+    it { expect(Uniqueness.generate(chars: 'ABCDEF')).to match(/^[A-F]+$/) }
   end
 end
diff --git a/spec/uniqueness/uniqueness_spec.rb b/spec/uniqueness/uniqueness_spec.rb
index d9b2411..6ed24e9 100644
--- a/spec/uniqueness/uniqueness_spec.rb
+++ b/spec/uniqueness/uniqueness_spec.rb
@@ -63,7 +63,7 @@
     end
   end
 
-  context 'intialized new object' do
+  context 'initialized new object' do
     it { expect(new_page.after_init_token).not_to be_nil }
 
     context 'length' do