diff --git a/src/option.h b/src/option.h
index b031466..7c7d35a 100644
--- a/src/option.h
+++ b/src/option.h
@@ -765,12 +765,13 @@
 EXTERN char_u	*p_swb;		/* 'switchbuf' */
 EXTERN unsigned	swb_flags;
 #ifdef IN_OPTION_C
-static char *(p_swb_values[]) = {"useopen", "usetab", "split", "newtab", NULL};
+static char *(p_swb_values[]) = {"useopen", "usetab", "split", "newtab", "vsplit", NULL};
 #endif
 #define SWB_USEOPEN		0x001
 #define SWB_USETAB		0x002
 #define SWB_SPLIT		0x004
 #define SWB_NEWTAB		0x008
+#define SWB_VSPLIT		0x010
 EXTERN int	p_tbs;		/* 'tagbsearch' */
 EXTERN long	p_tl;		/* 'taglength' */
 EXTERN int	p_tr;		/* 'tagrelative' */