diff --git a/libfreerdp-locale/timezone.c b/libfreerdp-locale/timezone.c
index b4e5fc31d..79782a032 100644
--- a/libfreerdp-locale/timezone.c
+++ b/libfreerdp-locale/timezone.c
@@ -1543,14 +1543,14 @@ boolean freerdp_match_unix_timezone_identifier_with_list(const char* tzid, const
 uint64 freerdp_get_windows_time_from_unix_time(time_t unix_time)
 {
 	uint64 windows_time;
-	windows_time = (unix_time * 10000000) + 621355968000000000;
+	windows_time = (unix_time * 10000000) + 621355968000000000ULL;
 	return windows_time;
 }
 
 time_t freerdp_get_unix_time_from_windows_time(uint64 windows_time)
 {
 	time_t unix_time;
-	unix_time = (windows_time - 621355968000000000) / 10000000;
+	unix_time = (windows_time - 621355968000000000ULL) / 10000000;
 	return unix_time;
 }