diff --git a/lib/shoulda/matchers/active_model/validate_exclusion_of_matcher.rb b/lib/shoulda/matchers/active_model/validate_exclusion_of_matcher.rb
index 512ed1c0..2d3918d5 100644
--- a/lib/shoulda/matchers/active_model/validate_exclusion_of_matcher.rb
+++ b/lib/shoulda/matchers/active_model/validate_exclusion_of_matcher.rb
@@ -88,7 +88,16 @@ module Shoulda
       def validate_exclusion_of(attr)
         ValidateExclusionOfMatcher.new(attr)
       end
-      alias_method :ensure_exclusion_of, :validate_exclusion_of
+
+      # @deprecated Use {#validate_exclusion_of} instead.
+      # @return [ValidateExclusionOfMatcher]
+      def ensure_exclusion_of(attr)
+        Shoulda::Matchers.warn_about_deprecated_method(
+          :ensure_exclusion_of,
+          :validate_exclusion_of
+        )
+        validate_exclusion_of(attr)
+      end
 
       # @private
       class ValidateExclusionOfMatcher < ValidationMatcher
diff --git a/spec/shoulda/matchers/active_model/validate_exclusion_of_matcher_spec.rb b/spec/shoulda/matchers/active_model/validate_exclusion_of_matcher_spec.rb
index 98138bc4..a8e02081 100644
--- a/spec/shoulda/matchers/active_model/validate_exclusion_of_matcher_spec.rb
+++ b/spec/shoulda/matchers/active_model/validate_exclusion_of_matcher_spec.rb
@@ -3,9 +3,17 @@ require 'spec_helper'
 describe Shoulda::Matchers::ActiveModel do
   describe '#ensure_exclusion_of' do
     it 'is aliased to #validate_exclusion_of' do
-      expect(method(:ensure_exclusion_of)).to eq(method(:validate_exclusion_of))
+      matchers.expects(:validate_exclusion_of).with(:attr)
+
+      silence_warnings do
+        matchers.ensure_exclusion_of(:attr)
+      end
     end
   end
+
+  def matchers
+    @_matchers ||= Object.new.extend(described_class)
+  end
 end
 
 describe Shoulda::Matchers::ActiveModel::ValidateExclusionOfMatcher do