diff --git a/src/semaphore.cpp b/src/semaphore.cpp
index 4c6f3cf..756f41e 100644
--- a/src/semaphore.cpp
+++ b/src/semaphore.cpp
@@ -78,7 +78,7 @@ namespace bx
 
 		dispatch_time_t dt = 0 > _msecs
 			? DISPATCH_TIME_FOREVER
-			: dispatch_time(DISPATCH_TIME_NOW, _msecs*1000000)
+			: dispatch_time(DISPATCH_TIME_NOW, int64_t(_msecs)*1000000)
 			;
 		return !dispatch_semaphore_wait(si->m_handle, dt);
 	}
@@ -98,7 +98,7 @@ namespace bx
 
 	void toTimespecMs(timespec& _ts, int32_t _msecs)
 	{
-		toTimespecNs(_ts, _msecs*1000000);
+		toTimespecNs(_ts, uint64_t(_msecs)*1000000);
 	}
 
 	void add(timespec& _ts, int32_t _msecs)