diff --git a/regexec.c b/regexec.c
index 47073dc720419..4b21a0cb2be25 100644
--- a/regexec.c
+++ b/regexec.c
@@ -615,8 +615,9 @@ S_isFOO_utf8_lc(pTHX_ const U8 classnum, const U8* character, const U8* e)
         case CC_ENUM_XDIGIT_:    return is_XDIGIT_high(character);
         case CC_ENUM_VERTSPACE_: return is_VERTWS_high(character);
         default:
-            return _invlist_contains_cp(PL_XPosix_ptrs[classnum],
-                                        utf8_to_uvchr_buf(character, e, NULL));
+            UV cp;
+            return    utf8_to_uv(character, e, &cp, NULL)
+                   && _invlist_contains_cp(PL_XPosix_ptrs[classnum], cp);
     }
     NOT_REACHED; /* NOTREACHED */
 }