diff --git a/src/vim.h b/src/vim.h
index 289ef3c..d2e22fe 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1029,6 +1029,7 @@
 #define ECMD_OLDBUF	0x04	// use existing buffer if it exists
 #define ECMD_FORCEIT	0x08	// ! used in Ex command
 #define ECMD_ADDBUF	0x10	// don't edit, just add to buffer list
+#define ECMD_ALTBUF	0x20	// like ECMD_ADDBUF and set the alternate file
 
 // for lnum argument in do_ecmd()
 #define ECMD_LASTL	(linenr_T)0	// use last position in loaded file