diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index b2870d0..5b34c8e 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -363,6 +363,7 @@
 # define ex_setfiletype		ex_ni
 #endif
 #ifndef FEAT_DIFF
+# define ex_diffoff		ex_ni
 # define ex_diffpatch		ex_ni
 # define ex_diffgetput		ex_ni
 # define ex_diffsplit		ex_ni