diff --git a/libowlps/libowlps.c b/libowlps/libowlps.c
index a8cb571..b1f3ae5 100644
--- a/libowlps/libowlps.c
+++ b/libowlps/libowlps.c
@@ -126,7 +126,7 @@ int owl_timestamp_now_ns(TIMESTAMP *now)
  */
 void owl_timestamp_round_to_ms(TIMESTAMP *now)
 {
-  now->tv_nsec = now->tv_nsec / 1000000 * 1000000 ;
+  now->tv_nsec = now->tv_nsec / 1000000u * 1000000u ;
 }
 
 
@@ -151,7 +151,7 @@ TIMESTAMP owl_timeval_to_timestamp(const struct timeval d)
 {
   TIMESTAMP res ;
   res.tv_sec = d.tv_sec ;
-  res.tv_nsec = d.tv_usec * 1000 ;
+  res.tv_nsec = d.tv_usec * 1000u ;
   return res ;
 }
 
@@ -162,7 +162,7 @@ TIMESTAMP owl_timeval_to_timestamp(const struct timeval d)
  */
 uint64_t owl_timestamp_to_ms(TIMESTAMP d)
 {
-  return d.tv_sec * 1000 + d.tv_nsec / 1000000 ;
+  return (uint64_t) d.tv_sec * 1000u + (uint64_t) d.tv_nsec / 1000000u ;
 }