diff --git a/lib/mspec/mocks/mock.rb b/lib/mspec/mocks/mock.rb
index 04bc1e0..c61ba35 100644
--- a/lib/mspec/mocks/mock.rb
+++ b/lib/mspec/mocks/mock.rb
@@ -19,7 +19,7 @@ def self.stubs
   end
 
   def self.replaced_name(key)
-    :"__mspec_#{key.first}_#{key.last}__"
+    :"__mspec_#{key.last}__"
   end
 
   def self.replaced_key(obj, sym)
diff --git a/spec/mocks/mock_spec.rb b/spec/mocks/mock_spec.rb
index a971e4c..7426e0f 100644
--- a/spec/mocks/mock_spec.rb
+++ b/spec/mocks/mock_spec.rb
@@ -22,7 +22,7 @@
 RSpec.describe Mock, ".replaced_name" do
   it "returns the name for a method that is being replaced by a mock method" do
     m = double('a fake id')
-    expect(Mock.replaced_name(Mock.replaced_key(m, :method_call))).to eq(:"__mspec_#{m.object_id}_method_call__")
+    expect(Mock.replaced_name(Mock.replaced_key(m, :method_call))).to eq(:"__mspec_method_call__")
   end
 end