Modified to allow other threads to run in a multithreaded environment.
diff --git a/Modules/sgimodule.c b/Modules/sgimodule.c
index fca4806..1951ad8 100644
--- a/Modules/sgimodule.c
+++ b/Modules/sgimodule.c
@@ -26,6 +26,7 @@
 
 #include "allobjects.h"
 #include "modsupport.h"
+#include "ceval.h"
 
 extern int sginap(long);
 
@@ -37,7 +38,9 @@
 	long ticks;
 	if (!getargs(args, "l", &ticks))
 		return NULL;
+	BGN_SAVE
 	sginap(ticks);
+	END_SAVE
 	INCREF(None);
 	return None;
 }