diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
index 2b8bd8978a..563f0ed34f 100644
--- a/libavformat/mxfdec.c
+++ b/libavformat/mxfdec.c
@@ -1736,7 +1736,7 @@ 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;
 }