diff --git a/src/util-stringbuf.h b/src/util-stringbuf.h
index e7957d27..0be24409 100644
--- a/src/util-stringbuf.h
+++ b/src/util-stringbuf.h
@@ -150,12 +150,12 @@ stringbuf_append_from_fd(struct stringbuf *b, int fd, size_t maxlen)
 static inline int
 stringbuf_append_string(struct stringbuf *b, const char *msg)
 {
-	int r = stringbuf_ensure_space(b, strlen(msg) + 1);
+	size_t slen = strlen(msg);
+
+	int r = stringbuf_ensure_space(b, slen + 1);
 	if (r < 0)
 		return r;
 
-	size_t slen = strlen(msg);
-
 	if (!b->data) /* cannot happen, but let's make scan-build happy */
 		abort();