diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index a45710b70a550962530af534542d60de828f4169..7a484c97e500cf6dab94a443729d242af5053d7f 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -221,8 +221,8 @@ extern unsigned char sane_ctype[256];
 #define isalpha(x) sane_istest(x,GIT_ALPHA)
 #define isalnum(x) sane_istest(x,GIT_ALPHA | GIT_DIGIT)
 #define isprint(x) sane_istest(x,GIT_PRINT)
-#define islower(x) (sane_istest(x,GIT_ALPHA) && sane_istest(x,0x20))
-#define isupper(x) (sane_istest(x,GIT_ALPHA) && !sane_istest(x,0x20))
+#define islower(x) (sane_istest(x,GIT_ALPHA) && (x & 0x20))
+#define isupper(x) (sane_istest(x,GIT_ALPHA) && !(x & 0x20))
 #define tolower(x) sane_case((unsigned char)(x), 0x20)
 #define toupper(x) sane_case((unsigned char)(x), 0)