diff --git a/pkg/metricstore/buffer.go b/pkg/metricstore/buffer.go
index 46eb5149..665d8012 100644
--- a/pkg/metricstore/buffer.go
+++ b/pkg/metricstore/buffer.go
@@ -237,9 +237,10 @@ func (b *buffer) free(t int64) (delme bool, n int) {
 		n += m
 		if delme {
 			b.prev.next = nil
-			if cap(b.prev.data) == BufferCap {
-				bufferPool.Put(b.prev)
+			if cap(b.prev.data) != BufferCap {
+				b.prev.data = make([]schema.Float, 0, BufferCap)
 			}
+			bufferPool.Put(b.prev)
 			b.prev = nil
 		}
 	}
diff --git a/pkg/metricstore/level.go b/pkg/metricstore/level.go
index bfa0ddf0..85c2ba7b 100644
--- a/pkg/metricstore/level.go
+++ b/pkg/metricstore/level.go
@@ -189,9 +189,10 @@ func (l *Level) free(t int64) (int, error) {
 			delme, m := b.free(t)
 			n += m
 			if delme {
-				if cap(b.data) == BufferCap {
-					bufferPool.Put(b)
+				if cap(b.data) != BufferCap {
+					b.data = make([]schema.Float, 0, BufferCap)
 				}
+				bufferPool.Put(b)
 				l.metrics[i] = nil
 			}
 		}