diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 107787a..07b4215 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -103,7 +103,7 @@
 #define CLOCK_SOURCE_VALID_FOR_HRES		0x20
 
 /* simplify initialization of mask field */
-#define CLOCKSOURCE_MASK(bits) (cycle_t)(bits<64 ? ((1ULL<<bits)-1) : -1)
+#define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
 
 /**
  * clocksource_khz2mult - calculates mult from khz and shift