diff --git a/libavformat/avidec.c b/libavformat/avidec.c
index 54c87a2559..8a0938d5dc 100644
--- a/libavformat/avidec.c
+++ b/libavformat/avidec.c
@@ -136,7 +136,7 @@ static inline int get_duration(AVIStream *ast, int len)
 static int get_riff(AVFormatContext *s, AVIOContext *pb)
 {
     AVIContext *avi = s->priv_data;
-    char header[8];
+    char header[8] = {0};
     int i;
 
     /* check RIFF header */