diff --git a/libavformat/mux.c b/libavformat/mux.c
index f01b82b2ba..bd50191b87 100644
--- a/libavformat/mux.c
+++ b/libavformat/mux.c
@@ -189,7 +189,7 @@ static int validate_codec_tag(AVFormatContext *s, AVStream *st)
     const AVCodecTag *avctag;
     int n;
     enum AVCodecID id = AV_CODEC_ID_NONE;
-    unsigned int tag  = 0;
+    int64_t tag  = -1;
 
     /**
      * Check that tag + id is in the table
@@ -212,7 +212,7 @@ static int validate_codec_tag(AVFormatContext *s, AVStream *st)
     }
     if (id != AV_CODEC_ID_NONE)
         return 0;
-    if (tag && (st->codec->strict_std_compliance >= FF_COMPLIANCE_NORMAL))
+    if (tag >= 0 && (st->codec->strict_std_compliance >= FF_COMPLIANCE_NORMAL))
         return 0;
     return 1;
 }