diff --git a/walker.c b/walker.c
index d95b007294..2c86e406f9 100644
--- a/walker.c
+++ b/walker.c
@@ -9,10 +9,14 @@
 
 static unsigned char current_commit_sha1[20];
 
-void walker_say(struct walker *walker, const char *fmt, const char *hex)
+void walker_say(struct walker *walker, const char *fmt, ...)
 {
-	if (walker->get_verbosely)
-		fprintf(stderr, fmt, hex);
+	if (walker->get_verbosely) {
+		va_list ap;
+		va_start(ap, fmt);
+		vfprintf(stderr, fmt, ap);
+		va_end(ap);
+	}
 }
 
 static void report_missing(const struct object *obj)
diff --git a/walker.h b/walker.h
index 95e5765484..a869013e85 100644
--- a/walker.h
+++ b/walker.h
@@ -19,7 +19,8 @@ struct walker {
 };
 
 /* Report what we got under get_verbosely */
-void walker_say(struct walker *walker, const char *, const char *);
+__attribute__((format (printf, 2, 3)))
+void walker_say(struct walker *walker, const char *fmt, ...);
 
 /* Load pull targets from stdin */
 int walker_targets_stdin(char ***target, const char ***write_ref);