diff --git a/utils/utils.go b/utils/utils.go
index a4d8ac25..347a331f 100644
--- a/utils/utils.go
+++ b/utils/utils.go
@@ -74,7 +74,11 @@ func ToStringKey(values ...interface{}) string {
 		case uint:
 			results[idx] = strconv.FormatUint(uint64(v), 10)
 		default:
-			results[idx] = fmt.Sprint(reflect.Indirect(reflect.ValueOf(v)).Interface())
+			results[idx] = "nil"
+			vv := reflect.ValueOf(v)
+			if vv.IsValid() && !vv.IsZero() {
+				results[idx] = fmt.Sprint(reflect.Indirect(vv).Interface())
+			}
 		}
 	}
 
diff --git a/utils/utils_test.go b/utils/utils_test.go
index d0486822..8ff42af8 100644
--- a/utils/utils_test.go
+++ b/utils/utils_test.go
@@ -48,8 +48,10 @@ func TestToStringKey(t *testing.T) {
 	}{
 		{[]interface{}{"a"}, "a"},
 		{[]interface{}{1, 2, 3}, "1_2_3"},
+		{[]interface{}{1, nil, 3}, "1_nil_3"},
 		{[]interface{}{[]interface{}{1, 2, 3}}, "[1 2 3]"},
 		{[]interface{}{[]interface{}{"1", "2", "3"}}, "[1 2 3]"},
+		{[]interface{}{[]interface{}{"1", nil, "3"}}, "[1 <nil> 3]"},
 	}
 	for _, c := range cases {
 		if key := ToStringKey(c.values...); key != c.key {