diff --git a/src/message.c b/src/message.c
index fe02aed..d90666f 100644
--- a/src/message.c
+++ b/src/message.c
@@ -1774,7 +1774,7 @@
     return retval;
 }
 
-#if defined(FEAT_EVAL) || defined(PROTO)
+#if defined(FEAT_EVAL) || defined(FEAT_SPELL) || defined(PROTO)
 /*
  * Return the lhs or rhs of a mapping, with the key codes turned into printable
  * strings, in an allocated string.