diff --git a/ext/opcache/Optimizer/pass1_5.c b/ext/opcache/Optimizer/pass1_5.c
index 5ab5bf400bd..8f76c63d966 100644
--- a/ext/opcache/Optimizer/pass1_5.c
+++ b/ext/opcache/Optimizer/pass1_5.c
@@ -274,7 +274,11 @@ if (ZEND_OPTIMIZER_PASS_1 & OPTIMIZATION_LEVEL) {
 								Z_STRVAL(op_array->literals[opline->op1.constant + 1].constant), 
 								Z_STRLEN(op_array->literals[opline->op1.constant].constant) + 1, 
 								Z_HASH_P(&op_array->literals[opline->op1.constant + 1].constant),
-								(void **)&pce) == FAILURE) {
+								(void **)&pce) == FAILURE ||
+								((*pce)->type == ZEND_INTERNAL_CLASS &&
+								 (*pce)->info.internal.module->type != MODULE_PERSISTENT) ||
+								((*pce)->type == ZEND_USER_CLASS &&
+								 ZEND_CE_FILENAME(*pce) != op_array->filename)) {
 							break;
 						}
 					}
diff --git a/ext/opcache/tests/bug66338.phpt b/ext/opcache/tests/bug66338.phpt
new file mode 100644
index 00000000000..cf0018df94e
--- /dev/null
+++ b/ext/opcache/tests/bug66338.phpt
@@ -0,0 +1,42 @@
+--TEST--
+Bug #66338 (Optimization binding of class constants is not safely opcacheable)
+--INI--
+opcache.enable=0
+--SKIPIF--
+<?php if (!extension_loaded('Zend OPcache') || php_sapi_name() != "cli") die("skip CLI only"); ?>
+--FILE--
+<?php
+$root  = str_replace('.php', "", __FILE__);
+$base  = basename( $root );
+
+file_put_contents( "$root-Officials.inc", '<?php 
+	class Officials { static function getLeader() { return LocalTerms::GOV_LEADER; } }
+	' );
+
+file_put_contents( "$root-clientUS.php", '<?php 
+	class LocalTerms { const GOV_LEADER = "Barack Hussein Obama II"; }
+	require "'.$root.'-Officials.inc";
+	printf( "The President of the USA is %s\n", Officials::getLeader() );
+	' );
+
+file_put_contents( "$root-clientUK.php", '<?php 
+	class LocalTerms { const GOV_LEADER = "David William Donald Cameron"; }
+	require "'.$root.'-Officials.inc";
+	printf( "The Prime Minister of the UK is %s\n", Officials::getLeader() );
+	' );
+
+include "php_cli_server.inc";
+$uri = sprintf("http://%s/%s", PHP_CLI_SERVER_ADDRESS, basename(__FILE__));
+$opt = -1;   # This test works if $opt = 0
+php_cli_server_start("-d opcache.enable=1 -d opcache.enable_cli=1 -d opcache.optimization_level=$opt -d opcache.file_update_protection=0" );
+
+echo file_get_contents("http://" . PHP_CLI_SERVER_ADDRESS . "/$base-clientUS.php" );
+echo file_get_contents("http://" . PHP_CLI_SERVER_ADDRESS . "/$base-clientUK.php" );
+
+unlink("$root-Officials.inc");
+unlink("$root-clientUS.php");
+unlink("$root-clientUK.php");
+?>
+--EXPECT--
+The President of the USA is Barack Hussein Obama II
+The Prime Minister of the UK is David William Donald Cameron