diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 0878cb5cba..484b5d6191 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -316,7 +316,7 @@ static int start_ebml_master_crc32(AVIOContext *pb, AVIOContext **dyn_cp, ebml_m
 {
     int ret;
 
-    if (ret = avio_open_dyn_buf(dyn_cp) < 0)
+    if ((ret = avio_open_dyn_buf(dyn_cp)) < 0)
         return ret;
 
     if (pb->seekable)