diff --git a/libraries/AP_HAL_PX4/Util.cpp b/libraries/AP_HAL_PX4/Util.cpp
index 078d24413d..03f01b8cdf 100644
--- a/libraries/AP_HAL_PX4/Util.cpp
+++ b/libraries/AP_HAL_PX4/Util.cpp
@@ -99,8 +99,8 @@ enum PX4Util::safety_state PX4Util::safety_switch_state(void)
 void PX4Util::set_system_clock(uint64_t time_utc_usec)
 {
     timespec ts;
-    ts.tv_sec = time_utc_usec/1.0e6f;
-    ts.tv_nsec = (time_utc_usec % 1000000) * 1000;
+    ts.tv_sec = time_utc_usec/1000000ULL;
+    ts.tv_nsec = (time_utc_usec % 1000000ULL) * 1000ULL;
     clock_settime(CLOCK_REALTIME, &ts);    
 }