diff --git a/lib/erb.rb b/lib/erb.rb
index ff30621041..878b494231 100644
--- a/lib/erb.rb
+++ b/lib/erb.rb
@@ -521,6 +521,7 @@ class ERB
 
       # Deprecated. Kept for backward compatibility.
       SimpleScanner2 = SimpleScanner # :nodoc:
+      deprecate_constant :SimpleScanner2
 
       class ExplicitScanner < Scanner # :nodoc:
         def scan