diff --git a/.travis.yml b/.travis.yml
index 4362cc6c06..1b6988f368 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,17 +3,15 @@ cache: packages
 sudo: true
 dist: trusty
 
-addons:
-  apt:
-    packages:
-      - libfreetype6
-
-r:
-- 3.1
-- 3.2
-- oldrel
-- release
-- devel
+# build matrix; turn on vdiffr only on r release
+matrix:
+  include:
+  - r: devel
+  - r: release
+    env: USE_VDIFFR=true
+  - r: oldrel
+  - r: 3.2
+  - r: 3.1
 
 # work around temporary travis + R 3.5 bug
 r_packages: devtools
@@ -21,9 +19,13 @@ r_packages: devtools
 # Install manually because dev vdiffr is not compatible with Appveyor yet
 r_github_packages: lionel-/vdiffr
 
+# environment variables set for all builds
 env:
   global:
+  # don't treat missing suggested packages as error
   - _R_CHECK_FORCE_SUGGESTS_=false
+  # switch off vdiffr by default
+  - USE_VDIFFR=false
 
 after_success:
   - Rscript -e 'covr::codecov()'
diff --git a/tests/testthat/helper-vdiffr.R b/tests/testthat/helper-vdiffr.R
index e0bca59e85..10d375015a 100644
--- a/tests/testthat/helper-vdiffr.R
+++ b/tests/testthat/helper-vdiffr.R
@@ -1,12 +1,16 @@
+# default is equal to whether NOT_CRAN is true or not
+enable_vdiffr <- identical(Sys.getenv("NOT_CRAN"), "true")
 
-enable_vdiffr <- TRUE
-
-if (!requireNamespace("vdiffr", quietly = TRUE) ||
-  utils::packageVersion("vdiffr") < "0.2.3.9000") {
+# disable or enable vdiffr based on the state of USE_VDIFFR, if set
+if (identical(Sys.getenv("USE_VDIFFR"), "true")) {
+  enable_vdiffr <- TRUE
+} else if (identical(Sys.getenv("USE_VDIFFR"), "false")) {
   enable_vdiffr <- FALSE
 }
 
-if (paste(R.Version()$major, R.Version()$minor, sep = ".") < "3.3.0") {
+# disable vdiffr if version is too old
+if (!requireNamespace("vdiffr", quietly = TRUE) ||
+  utils::packageVersion("vdiffr") < "0.2.3.9000") {
   enable_vdiffr <- FALSE
 }