diff --git a/src/if_py_both.h b/src/if_py_both.h
index 5ecc239..c02cce3 100644
--- a/src/if_py_both.h
+++ b/src/if_py_both.h
@@ -3547,7 +3547,7 @@
     int		status;
     PyObject	*pyfunc, *pymain;
 
-    if (u_save(RangeStart - 1, RangeEnd + 1) != OK)
+    if (u_save((linenr_T)RangeStart - 1, (linenr_T)RangeEnd + 1) != OK)
     {
 	EMSG(_("cannot save undo information"));
 	return;