diff --git a/src/common.h b/src/common.h
index ae0cfe8a9..0ba47f3bc 100644
--- a/src/common.h
+++ b/src/common.h
@@ -310,8 +310,8 @@ void wcs2string_appending(const wchar_t *in, size_t len, std::string *receiver);
 bool should_suppress_stderr_for_tests();
 
 /// Branch prediction hints. Idea borrowed from Linux kernel. Just used for asserts.
-#define likely(x) __builtin_expect(!!(x), 1)
-#define unlikely(x) __builtin_expect(!!(x), 0)
+#define likely(x) __builtin_expect(bool(x), 1)
+#define unlikely(x) __builtin_expect(bool(x), 0)
 
 void assert_is_main_thread(const char *who);
 #define ASSERT_IS_MAIN_THREAD_TRAMPOLINE(x) assert_is_main_thread(x)