diff --git a/rtmp/rtmp.go b/rtmp/rtmp.go
index f1226f01..7a66a6a1 100644
--- a/rtmp/rtmp.go
+++ b/rtmp/rtmp.go
@@ -2189,7 +2189,7 @@ func C_RTMP_Write(r *C_RTMP, buf []byte) int {
 				return -1
 			}
 			if len(buf) < 4 {
-				break
+				return size + (len(buf) - 4)
 			}
 			buf = buf[4:]
 		}