diff --git a/contrib/file/compress.c b/contrib/file/compress.c
index 4308abfaa3ab..2d8d77f2cb35 100644
--- a/contrib/file/compress.c
+++ b/contrib/file/compress.c
@@ -480,7 +480,7 @@ uncompressbuf(struct magic_set *ms, int fd, size_t method,
 #endif
 			free(*newch);
 			n = 0;
-			newch[0] = '\0';
+			*newch = NULL;
 			goto err;
 		} else {
 			n = r;