Need mytime.h for Sleep().
diff --git a/Modules/_tkinter.c b/Modules/_tkinter.c
index 8a09dd6..8f1e4f7 100644
--- a/Modules/_tkinter.c
+++ b/Modules/_tkinter.c
@@ -281,6 +281,8 @@
 
 #ifdef WITH_THREAD
 #ifndef MS_WINDOWS
+#include "mytime.h"
+
 /* Millisecond sleep() for Unix platforms. */
 
 static void