diff --git a/activesupport/lib/active_support/core_ext/hash/diff.rb b/activesupport/lib/active_support/core_ext/hash/diff.rb
index a27c55479a..5f3868b5b0 100644
--- a/activesupport/lib/active_support/core_ext/hash/diff.rb
+++ b/activesupport/lib/active_support/core_ext/hash/diff.rb
@@ -6,7 +6,7 @@ class Hash
   #   {}.diff(1 => 2)               # => {1 => 2}
   #   {1 => 2, 3 => 4}.diff(1 => 2) # => {3 => 4}
   def diff(other)
-    ActiveSupport::Deprecation.warn "Hash#diff is no longer used inside of Rails, and is being deprecated with no replacement. If you're using it to compare hashes for the purpose of testing, please use MiniTest's diff instead."
+    ActiveSupport::Deprecation.warn "Hash#diff is no longer used inside of Rails, and is being deprecated with no replacement. If you're using it to compare hashes for the purpose of testing, please use MiniTest's assert_equal instead."
     dup.
       delete_if { |k, v| other[k] == v }.
       merge!(other.dup.delete_if { |k, v| has_key?(k) })