diff --git a/src/diff.c b/src/diff.c
index 4acba3d..3265986 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -1009,6 +1009,7 @@
     {
 	/* Pretend it was a ":split fname" command */
 	eap->cmdidx = CMD_split;
+	curwin->w_p_diff = TRUE;
 	do_exedit(eap, old_curwin);
 
 	if (curwin != old_curwin)		/* split must have worked */