diff --git a/lib/shoulda/matchers/active_model/validate_inclusion_of_matcher.rb b/lib/shoulda/matchers/active_model/validate_inclusion_of_matcher.rb
index 4b96be052..f152cb540 100644
--- a/lib/shoulda/matchers/active_model/validate_inclusion_of_matcher.rb
+++ b/lib/shoulda/matchers/active_model/validate_inclusion_of_matcher.rb
@@ -310,8 +310,8 @@ def in_range(range)
           self
         end
 
-        def allow_blank(allow_blank = true)
-          @options[:allow_blank] = allow_blank
+        def allow_blank
+          @options[:allow_blank] = true
           self
         end
 
@@ -319,9 +319,8 @@ def expects_to_allow_blank?
           @options[:allow_blank]
         end
 
-        def allow_nil(allow_nil = true)
-          @options[:allow_nil] = allow_nil
-          self
+        def allow_nil
+          @options[:allow_nil] = true
         end
 
         def expects_to_allow_nil?