diff --git a/src/simulator/nstime.h b/src/simulator/nstime.h
index b968ea70c..0bff74292 100644
--- a/src/simulator/nstime.h
+++ b/src/simulator/nstime.h
@@ -368,7 +368,7 @@ class MicroSeconds : public TimeUnit<1>
 {
 public:
   MicroSeconds ();
-  MicroSeconds (uint32_t ms);
+  MicroSeconds (uint64_t ms);
 };
 /**
  * \brief create ns3::Time instances in units of nanoseconds.
@@ -383,7 +383,7 @@ class NanoSeconds : public TimeUnit<1>
 {
 public:
   NanoSeconds ();
-  NanoSeconds (uint32_t ms);
+  NanoSeconds (uint64_t ms);
 };
 
 /**
diff --git a/src/simulator/time.cc b/src/simulator/time.cc
index 0bdb1f641..d0da4476f 100644
--- a/src/simulator/time.cc
+++ b/src/simulator/time.cc
@@ -73,13 +73,13 @@ MilliSeconds::MilliSeconds (uint32_t ms)
 MicroSeconds::MicroSeconds ()
   : TimeUnit<1> ()
 {}
-MicroSeconds::MicroSeconds (uint32_t us)
+MicroSeconds::MicroSeconds (uint64_t us)
   : TimeUnit<1> (HighPrecision (us * 1000, false))
 {}
 NanoSeconds::NanoSeconds ()
   : TimeUnit<1> ()
 {}
-NanoSeconds::NanoSeconds (uint32_t ns)
+NanoSeconds::NanoSeconds (uint64_t ns)
   : TimeUnit<1> (HighPrecision (ns, false))
 {}