diff --git a/mock/mock.go b/mock/mock.go
index 746151e1b..cdb665a84 100644
--- a/mock/mock.go
+++ b/mock/mock.go
@@ -666,8 +666,8 @@ func (m *Mock) AssertNumberOfCalls(t TestingT, methodName string, expectedCalls
 	m.mutex.Lock()
 	defer m.mutex.Unlock()
 	var actualCalls int
-	for _, call := range m.calls() {
-		if call.Method == methodName {
+	for i := range m.Calls {
+		if m.Calls[i].Method == methodName {
 			actualCalls++
 		}
 	}
diff --git a/mock/mock_test.go b/mock/mock_test.go
index c30f526c4..92c1595d5 100644
--- a/mock/mock_test.go
+++ b/mock/mock_test.go
@@ -1744,6 +1744,23 @@ func Test_Mock_AssertNumberOfCalls(t *testing.T) {
 
 }
 
+func Benchmark_Mock_AssertNumberOfCalls(b *testing.B) {
+	b.ReportAllocs()
+
+	m := new(Mock)
+	m.On("BenchmarkMethod", 1).Return()
+	for i := 0; i < 100; i++ {
+		m.MethodCalled("BenchmarkMethod", 1)
+	}
+
+	t := new(testing.T)
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		m.AssertNumberOfCalls(t, "BenchmarkMethod", 100)
+	}
+}
+
 func Test_Mock_AssertCalled(t *testing.T) {
 	t.Parallel()