diff --git a/tools/perf/util/string.c b/tools/perf/util/string.c
index d8dfaf64b32e19af441b121803e4b4418d31c69e..bddca519dd5854a0fd3319e85d54d7e638514b47 100644
--- a/tools/perf/util/string.c
+++ b/tools/perf/util/string.c
@@ -21,6 +21,8 @@ s64 perf_atoll(const char *str)
 		case 'b': case 'B':
 			if (*p)
 				goto out_err;
+
+			__fallthrough;
 		case '\0':
 			return length;
 		default: