2 files changed, 5 insertions, 4 deletions
diff --git a/activemodel/lib/active_model/validations/clusivity.rb b/activemodel/lib/active_model/validations/clusivity.rb
index 49df98d6c1..c5aacb010a 100644
--- a/activemodel/lib/active_model/validations/clusivity.rb
+++ b/activemodel/lib/active_model/validations/clusivity.rb
@@ -31,10 +31,11 @@ module ActiveModel
       end
 
       # In Ruby 1.9 <tt>Range#include?</tt> on non-numeric ranges checks all possible values in the
-      # range for equality, so it may be slow for large ranges. The new <tt>Range#cover?</tt>
-      # uses the previous logic of comparing a value with the range endpoints.
+      # range for equality, which is slower but more accurate. <tt>Range#cover?</tt> uses
+      # the previous logic of comparing a value with the range endpoints, which is fast
+      # but is only accurate on numeric ranges.
       def inclusion_method(enumerable)
-        enumerable.is_a?(Range) ? :cover? : :include?
+        (enumerable.is_a?(Range) && enumerable.first.is_a?(Numeric)) ? :cover? : :include?
       end
     end
   end
diff --git a/activemodel/lib/active_model/validations/inclusion.rb b/activemodel/lib/active_model/validations/inclusion.rb
index 1cfd86efee..24337614c5 100644
--- a/activemodel/lib/active_model/validations/inclusion.rb
+++ b/activemodel/lib/active_model/validations/inclusion.rb
@@ -28,7 +28,7 @@ module ActiveModel
       # Configuration options:
       # * <tt>:in</tt> - An enumerable object of available items. This can be
       #   supplied as a proc, lambda or symbol which returns an enumerable. If the
-      #   enumerable is a range the test is performed with <tt>Range#cover?</tt>,
+      #   enumerable is a numerical range the test is performed with <tt>Range#cover?</tt>,
       #   otherwise with <tt>include?</tt>.
       # * <tt>:within</tt> - A synonym(or alias) for <tt>:in</tt>
       # * <tt>:message</tt> - Specifies a custom error message (default is: "is