diff --git a/src/globals.h b/src/globals.h
index 81c1f7e..bbb0f1a 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1297,7 +1297,7 @@
 #endif
 EXTERN char_u e_invrange[]	INIT(=N_("E16: Invalid range"));
 EXTERN char_u e_invcmd[]	INIT(=N_("E476: Invalid command"));
-#ifdef UNIX
+#if defined(UNIX) || (defined(FEAT_SYN_HL) && defined(FEAT_MBYTE))
 EXTERN char_u e_isadir2[]	INIT(=N_("E17: \"%s\" is a directory"));
 #endif
 #ifdef FEAT_LIBCALL