diff --git a/src/vim.h b/src/vim.h
index 91ef5cc..4174fa0 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1250,6 +1250,7 @@
 #define SEA_DIALOG	1	// use dialog when possible
 #define SEA_QUIT	2	// quit editing the file
 #define SEA_RECOVER	3	// recover the file
+#define SEA_READONLY	4	// no dialog, mark buffer as read-only
 
 /*
  * Minimal size for block 0 of a swap file.