diff --git a/libavformat/ffmdec.c b/libavformat/ffmdec.c
index 987f419c96..280a24cb38 100644
--- a/libavformat/ffmdec.c
+++ b/libavformat/ffmdec.c
@@ -261,7 +261,7 @@ static int ffm2_read_header(AVFormatContext *s)
     AVIOContext *pb = s->pb;
     AVCodecContext *codec;
     int ret;
-    int f_main = 0, f_cprv, f_stvi, f_stau;
+    int f_main = 0, f_cprv = -1, f_stvi = -1, f_stau = -1;
     AVCodec *enc;
     char *buffer;