diff --git a/activesupport/lib/active_support/testing/assertions.rb b/activesupport/lib/active_support/testing/assertions.rb
index ba34e9853c7568d5a94aa5cb898060b034ab4e3c..f3629ada5b8542006055680f1b896ec380af9449 100644
--- a/activesupport/lib/active_support/testing/assertions.rb
+++ b/activesupport/lib/active_support/testing/assertions.rb
@@ -45,18 +45,19 @@ module Assertions
       #     post :delete, :id => ...
       #   end
       def assert_difference(expression, difference = 1, message = nil, &block)
-        exps = Array.wrap(expression).map { |e|
-          callee = e.respond_to?(:call) ? e : lambda { eval(e, block.binding) }
-          [e, callee]
+        expressions = Array.wrap expression
+
+        exps = expressions.map { |e|
+          e.respond_to?(:call) ? e : lambda { eval(e, block.binding) }
         }
-        before = exps.map { |_, block| block.call }
+        before = exps.map { |e| e.call }
 
         yield
 
-        exps.each_with_index do |(code, block), i|
+        expressions.zip(exps).each_with_index do |(code, e), i|
           error  = "#{code.inspect} didn't change by #{difference}"
           error  = "#{message}.\n#{error}" if message
-          assert_equal(before[i] + difference, block.call, error)
+          assert_equal(before[i] + difference, e.call, error)
         end
       end