diff --git a/server/client.go b/server/client.go
index 1c4725282f..e3364c8a80 100644
--- a/server/client.go
+++ b/server/client.go
@@ -346,23 +346,20 @@ func nbPoolGet(sz int) []byte {
 	}
 }
 
-func nbPoolPut(in []byte) {
-	ca := cap(in)
-	for in = in[:ca]; ca >= nbPoolSizeSmall; ca = cap(in) {
-		switch {
-		case ca >= nbPoolSizeLarge:
-			b := (*[nbPoolSizeLarge]byte)(in[0:nbPoolSizeLarge:nbPoolSizeLarge])
-			nbPoolLarge.Put(b)
-			in = in[nbPoolSizeLarge:]
-		case ca >= nbPoolSizeMedium:
-			b := (*[nbPoolSizeMedium]byte)(in[0:nbPoolSizeMedium:nbPoolSizeMedium])
-			nbPoolMedium.Put(b)
-			in = in[nbPoolSizeMedium:]
-		case ca >= nbPoolSizeSmall:
-			b := (*[nbPoolSizeSmall]byte)(in[0:nbPoolSizeSmall:nbPoolSizeSmall])
-			nbPoolSmall.Put(b)
-			in = in[nbPoolSizeSmall:]
-		}
+func nbPoolPut(b []byte) {
+	switch cap(b) {
+	case nbPoolSizeSmall:
+		b := (*[nbPoolSizeSmall]byte)(b[0:nbPoolSizeSmall])
+		nbPoolSmall.Put(b)
+	case nbPoolSizeMedium:
+		b := (*[nbPoolSizeMedium]byte)(b[0:nbPoolSizeMedium])
+		nbPoolMedium.Put(b)
+	case nbPoolSizeLarge:
+		b := (*[nbPoolSizeLarge]byte)(b[0:nbPoolSizeLarge])
+		nbPoolLarge.Put(b)
+	default:
+		// Ignore frames that are the wrong size, this might happen
+		// with WebSocket/MQTT messages as they are framed
 	}
 }
 
diff --git a/server/websocket.go b/server/websocket.go
index 8163568d05..014a1d72fc 100644
--- a/server/websocket.go
+++ b/server/websocket.go
@@ -1345,6 +1345,11 @@ func (c *client) wsCollapsePtoNB() (net.Buffers, int64) {
 			}
 			csz = len(h) + ol
 		}
+		// Make sure that the compressor no longer holds a reference to
+		// the bytes.Buffer, so that the underlying memory gets cleaned
+		// up after flushOutbound/flushAndClose. For this to be safe, we
+		// always cp.Reset(...) before reusing the compressor again.
+		cp.Reset(nil)
 		// Add to pb the compressed data size (including headers), but
 		// remove the original uncompressed data size that was added
 		// during the queueing.