diff --git a/lib/phlex/elements.rb b/lib/phlex/elements.rb
index 50e3c3c4..4a5e1bd3 100644
--- a/lib/phlex/elements.rb
+++ b/lib/phlex/elements.rb
@@ -28,13 +28,20 @@ def registered_elements
 	# @note The methods defined by this macro depend on other methods from {SGML} so they should always be mixed into an {HTML} or {SVG} component.
 	# @example Register the custom element `<trix-editor>`
 	# 	register_element :trix_editor
-	def register_element(method_name, tag: nil, deprecated: false)
-		tag ||= method_name.name.tr("_", "-")
+	def register_element(method_name, tag: method_name.name.tr("_", "-"), deprecated: false)
+		if deprecated
+			deprecation = <<~RUBY
+				Kernel.warn "#{deprecated}"
+			RUBY
+		else
+			deprecation = ""
+		end
 
 		class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
 			# frozen_string_literal: true
 
 			def #{method_name}(**attributes, &block)
+				#{deprecation}
 				target = @_context.target
 
 				if attributes.length > 0 # with attributes
@@ -70,10 +77,19 @@ def #{method_name}(**attributes, &block)
 
 	# @api private
 	def register_void_element(method_name, tag: method_name.name.tr("_", "-"), deprecated: false)
+		if deprecated
+			deprecation = <<~RUBY
+				Kernel.warn "#{deprecated}"
+			RUBY
+		else
+			deprecation = ""
+		end
+
 		class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
 			# frozen_string_literal: true
 
 			def #{method_name}(**attributes)
+				#{deprecation}
 				target = @_context.target
 
 				if attributes.length > 0 # with attributes
diff --git a/lib/phlex/html/void_elements.rb b/lib/phlex/html/void_elements.rb
index c237cce2..2a7d21c8 100644
--- a/lib/phlex/html/void_elements.rb
+++ b/lib/phlex/html/void_elements.rb
@@ -62,7 +62,7 @@ module Phlex::HTML::VoidElements
 	# 	Outputs a `<param>` tag.
 	# 	@return [nil]
 	# 	@see https://developer.mozilla.org/docs/Web/HTML/Element/param
-	register_void_element :param, deprecated: true
+	register_void_element :param, deprecated: "The <param> tag is deprecated. See https://developer.mozilla.org/en-US/docs/Web/HTML/Element/param"
 
 	# @!method source(**attributes, &content)
 	# 	Outputs a `<source>` tag.