diff --git a/src/spell.h b/src/spell.h
index b444145..7e4f813 100644
--- a/src/spell.h
+++ b/src/spell.h
@@ -66,6 +66,7 @@
     int		sl_add;		// TRUE if it's a .add file.
 
     char_u	*sl_fbyts;	// case-folded word bytes
+    long	sl_fbyts_len;	// length of sl_fbyts
     idx_T	*sl_fidxs;	// case-folded word indexes
     char_u	*sl_kbyts;	// keep-case word bytes
     idx_T	*sl_kidxs;	// keep-case word indexes