diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
index 2e8dd05ab4..e8fa7312a1 100644
--- a/libavformat/mxfdec.c
+++ b/libavformat/mxfdec.c
@@ -2041,7 +2041,7 @@ static int mxf_timestamp_to_str(uint64_t timestamp, char **str)
     if (!*str)
         return AVERROR(ENOMEM);
     if (!strftime(*str, 32, "%Y-%m-%d %H:%M:%S", &time))
-        str[0] = '\0';
+        (*str)[0] = '\0';
 
     return 0;
 }