diff --git a/cache_test.go b/cache_test.go
index 5a3b396..e30adc7 100644
--- a/cache_test.go
+++ b/cache_test.go
@@ -1457,6 +1457,21 @@ func BenchmarkRWMutexMapGet(b *testing.B) {
 	}
 }
 
+func BenchmarkRWMutexInterfaceMapGet(b *testing.B) {
+	b.StopTimer()
+	s := struct{name string}{name: "foo"}
+	m := map[interface{}]string{
+		s: "bar",
+	}
+	mu := sync.RWMutex{}
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		mu.RLock()
+		_, _ = m[s]
+		mu.RUnlock()
+	}
+}
+
 func BenchmarkCacheGetConcurrentExpiring(b *testing.B) {
 	benchmarkCacheGetConcurrent(b, 5*time.Minute)
 }