diff --git a/src/quickfix.c b/src/quickfix.c
index 3b47132..1ae175b 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -2331,7 +2331,7 @@
 	    set_option_value((char_u *)"bt", 0L, (char_u *)"quickfix",
 								   OPT_LOCAL);
 	    set_option_value((char_u *)"bh", 0L, (char_u *)"wipe", OPT_LOCAL);
-	    set_option_value((char_u *)"diff", 0L, (char_u *)"", OPT_LOCAL);
+	    set_option_value((char_u *)"diff", 0L, NULL, OPT_LOCAL);
 	}
 
 	/* Only set the height when still in the same tab page and there is no