diff --git a/vm/os-windows-nt.cpp b/vm/os-windows-nt.cpp
index cdb0dad350..3feabfe8bc 100755
--- a/vm/os-windows-nt.cpp
+++ b/vm/os-windows-nt.cpp
@@ -48,7 +48,7 @@ u64 current_nanos()
 	if(ret == 0)
 		fatal_error("QueryPerformanceFrequency", 0);
 	
-	return (ulonglong)count*(1000000000/frequency);
+	return count.QuadPart*(1000000000/frequency.QuadPart);
 }
 
 LONG factor_vm::exception_handler(PEXCEPTION_POINTERS pe)
diff --git a/vm/os-windows.hpp b/vm/os-windows.hpp
index 403842b2cb..fd24120b95 100644
--- a/vm/os-windows.hpp
+++ b/vm/os-windows.hpp
@@ -44,6 +44,7 @@ inline static void init_signals() {}
 inline static void early_init() {}
 
 s64 current_micros();
+u64 current_nanos();
 long getpagesize();
 
 }