diff --git a/src/structs.h b/src/structs.h
index 7deb5ab..25012d6 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1166,7 +1166,8 @@
     char_u	*b_fname;	/* current file name */
 
 #ifdef UNIX
-    dev_t	b_dev;		/* device number (-1 if not set) */
+    int		b_dev_valid;	/* TRUE when b_dev has a valid number */
+    dev_t	b_dev;		/* device number */
     ino_t	b_ino;		/* inode number */
 #endif
 #ifdef FEAT_CW_EDITOR