diff --git a/rtmp/packet.go b/rtmp/packet.go
index 0f3ae241..a92f7022 100644
--- a/rtmp/packet.go
+++ b/rtmp/packet.go
@@ -199,9 +199,7 @@ func (pkt *packet) readFrom(c *Conn) error {
 		hSize += 4
 	}
 
-	if pkt.bodySize > 0 && pkt.body == nil {
-		pkt.resize(pkt.bodySize, (hbuf[0]&0xc0)>>6)
-	}
+	pkt.resize(pkt.bodySize, pkt.headerType)
 
 	if pkt.bodySize > c.inChunkSize {
 		c.log(WarnLevel, pkg+"reading large packet", "size", int(pkt.bodySize))
@@ -234,10 +232,12 @@ func (pkt *packet) readFrom(c *Conn) error {
 	return nil
 }
 
-// resize adjusts the packet's storage to accommodate a body of the given size and header type.
+// resize adjusts the packet's storage (if necessary) to accommodate a body of the given size and header type.
 // When headerSizeAuto is specified, the header type is computed based on packet type.
 func (pkt *packet) resize(size uint32, ht uint8) {
-	pkt.buf = make([]byte, fullHeaderSize+size)
+	if cap(pkt.buf) < fullHeaderSize+int(size) {
+		pkt.buf = make([]byte, fullHeaderSize+size)
+	}
 	pkt.body = pkt.buf[fullHeaderSize:]
 	if ht != headerSizeAuto {
 		pkt.headerType = ht