diff --git a/src/structs.h b/src/structs.h
index 2ec02f3..927aa06 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1200,7 +1200,7 @@
 
     long	b_mtime;	/* last change time of original file */
     long	b_mtime_read;	/* last change time when reading */
-    size_t	b_orig_size;	/* size of original file in bytes */
+    off_t	b_orig_size;	/* size of original file in bytes */
     int		b_orig_mode;	/* mode of original file */
 
     pos_T	b_namedm[NMARKS]; /* current named marks (mark.c) */