diff --git a/src/Onigmo/regext.c b/src/Onigmo/regext.c
index 21ffd5a..28c6946 100644
--- a/src/Onigmo/regext.c
+++ b/src/Onigmo/regext.c
@@ -170,9 +170,7 @@ onig_new_deluxe(regex_t** reg, const UChar* pattern, const UChar* pattern_end,
   if (IS_NOT_NULL(einfo)) einfo->par = (UChar* )NULL;
 
   if (ci->pattern_enc != ci->target_enc) {
-    r = conv_encoding(ci->pattern_enc, ci->target_enc, pattern, pattern_end,
-                      &cpat, &cpat_end);
-    if (r) return r;
+    return ONIGERR_NOT_SUPPORTED_ENCODING_COMBINATION;
   }
   else {
     cpat     = (UChar* )pattern;