diff --git a/src/regexp_nfa.c b/src/regexp_nfa.c
index 0ead03a..e629699 100644
--- a/src/regexp_nfa.c
+++ b/src/regexp_nfa.c
@@ -1482,7 +1482,7 @@
 		case '8':
 		case '9':
 		    /* \z1...\z9 */
-		    if (reg_do_extmatch != REX_USE)
+		    if ((reg_do_extmatch & REX_USE) == 0)
 			EMSG_RET_FAIL(_(e_z1_not_allowed));
 		    EMIT(NFA_ZREF1 + (no_Magic(c) - '1'));
 		    /* No need to set nfa_has_backref, the sub-matches don't
@@ -1491,7 +1491,7 @@
 		    break;
 		case '(':
 		    /* \z(  */
-		    if (reg_do_extmatch != REX_SET)
+		    if ((reg_do_extmatch & REX_SET) == 0)
 			EMSG_RET_FAIL(_(e_z_not_allowed));
 		    if (nfa_reg(REG_ZPAREN) == FAIL)
 			return FAIL;	    /* cascaded error */
@@ -5692,7 +5692,8 @@
 	nextlist->n = 0;	    /* clear nextlist */
 	nextlist->has_pim = FALSE;
 	++nfa_listid;
-	if (prog->re_engine == AUTOMATIC_ENGINE && nfa_listid >= NFA_MAX_STATES)
+	if (prog->re_engine == AUTOMATIC_ENGINE
+		&& (nfa_listid >= NFA_MAX_STATES || nfa_fail_for_testing))
 	{
 	    /* too many states, retry with old engine */
 	    nfa_match = NFA_TOO_EXPENSIVE;