diff --git a/opcode.h b/opcode.h
index 8f040e1813c9..d824e17db15c 100644
--- a/opcode.h
+++ b/opcode.h
@@ -1869,8 +1869,26 @@ INIT({
 	Perl_ck_null,		/* methstart */
 	Perl_ck_null,		/* initfield */
 	Perl_ck_classname,	/* classname */
+
+/* The final entries are function pointers not attached to an opcode.
+ * These are used to compare with function pointers in the earlier part of
+ * the array, since in some platforms (notably z/OS), it is undefined
+ * behavior to compare function pointers for equality, even though calling
+ * them will invoke the same function.  This minimizes the risk of them
+ * being different by initializing them to the same values in the same
+ * array. */
+	Perl_ck_null,
+		Perl_ck_exists,
+	Perl_ck_delete,
 });
 
+/* Indexes into PL_check for the comparison function pointers */
+#ifdef PERL_IN_PEEP_C
+  #define PERL_CK_NULL  426
+  #define PERL_CK_EXISTS  427
+  #define PERL_CK_DELETE  428
+#endif
+
 EXTCONST U32 PL_opargs[] INIT({
 	0x00000000,	/* null */
 	0x00000000,	/* stub */
diff --git a/peep.c b/peep.c
index 5980ea1c2fca..a73deff1cf76 100644
--- a/peep.c
+++ b/peep.c
@@ -2203,16 +2203,20 @@ S_maybe_multideref(pTHX_ OP *start, OP *orig_o, UV orig_action, U8 hints)
              * OP_EXISTS or OP_DELETE */
 
             /* if a custom array/hash access checker is in scope,
-             * abandon optimisation attempt */
+             * abandon optimisation attempt.  Check two different ways because
+             * of z/OS (see comments in opcode.h) */
             if (  (o->op_type == OP_AELEM || o->op_type == OP_HELEM)
-               && PL_check[o->op_type] != Perl_ck_null)
+               && UNLIKELY(PL_check[o->op_type] != Perl_ck_null)
+               && UNLIKELY(PL_check[o->op_type] != PL_check[PERL_CK_NULL]))
                 return;
             /* similarly for customised exists and delete */
             if (  (o->op_type == OP_EXISTS)
-               && PL_check[o->op_type] != Perl_ck_exists)
+               && UNLIKELY(PL_check[OP_EXISTS] != Perl_ck_exists)
+               && UNLIKELY(PL_check[OP_EXISTS] != PL_check[PERL_CK_EXISTS]))
                 return;
             if (  (o->op_type == OP_DELETE)
-               && PL_check[o->op_type] != Perl_ck_delete)
+               && UNLIKELY(PL_check[OP_DELETE] != Perl_ck_delete)
+               && UNLIKELY(PL_check[OP_DELETE] != PL_check[PERL_CK_DELETE]))
                 return;
 
             if (   o->op_type != OP_AELEM
diff --git a/regen/opcode.pl b/regen/opcode.pl
index d59ed7c7d73f..e0301a3cc062 100755
--- a/regen/opcode.pl
+++ b/regen/opcode.pl
@@ -1114,13 +1114,39 @@ sub generate_opcode_h_pl_check {
     INIT({
     END
 
+
     for (@ops) {
         print "\t", tab(3, "Perl_$check{$_},"), "\t/* $_ */\n";
     }
 
+    print <<~'END';
+
+    /* The final entries are function pointers not attached to an opcode.
+     * These are used to compare with function pointers in the earlier part of
+     * the array, since in some platforms (notably z/OS), it is undefined
+     * behavior to compare function pointers for equality, even though calling
+     * them will invoke the same function.  This minimizes the risk of them
+     * being different by initializing them to the same values in the same
+     * array. */
+    END
+    my @perl_internal_extras = qw(ck_null ck_exists ck_delete);
+    for (@perl_internal_extras) {
+        print "\t", tab(3, "Perl_$_,\n");
+    }
+
     print <<~'END';
     });
+
+    /* Indexes into PL_check for the comparison function pointers */
+    #ifdef PERL_IN_PEEP_C
     END
+
+    for (my $i = 0; $i < @perl_internal_extras; $i++) {
+        my $index = @ops + $i;
+        my $define = uc $perl_internal_extras[$i];
+        print "  #define PERL_$define  $index\n";
+    }
+    print "#endif\n";
 }
 
 sub generate_opcode_h_pl_opargs {