diff --git a/lib/System/Win32/Alarm.inc b/lib/System/Win32/Alarm.inc
index 64a2107..dca9e08 100644
--- a/lib/System/Win32/Alarm.inc
+++ b/lib/System/Win32/Alarm.inc
@@ -35,6 +35,9 @@
   return 0;
 }
 
-void Sleep(unsigned n) {
+// Don't pull in all of the Windows headers.
+extern "C" _stdcall void Sleep(unsigned long);
+
+void sys::Sleep(unsigned n) {
   Sleep(n*1000);
 }