diff --git a/internal/observability/metrics/mem/mem.go b/internal/observability/metrics/mem/mem.go
index 513e9eeced9..d817e1fe97b 100644
--- a/internal/observability/metrics/mem/mem.go
+++ b/internal/observability/metrics/mem/mem.go
@@ -1,16 +1,18 @@
+//
 // Copyright (C) 2019-2023 vdaas.org vald team <vald@vdaas.org>
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // You may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
-//	https://www.apache.org/licenses/LICENSE-2.0
+//    https://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+//
 package mem
 
 import (
@@ -603,7 +605,10 @@ func (mm *memMetrics) Register(m metrics.Meter) error {
 			runtime.ReadMemStats(&mstats)
 
 			for i, instrument := range instruments {
-				instrument.(asyncint64.Gauge).Observe(ctx, mInfo[i].Value())
+				g, ok := instrument.(asyncint64.Gauge)
+				if ok {
+					g.Observe(ctx, mInfo[i].Value())
+				}
 			}
 		},
 	)