diff --git a/Zend/tests/gh16630.phpt b/Zend/tests/gh16630.phpt
new file mode 100644
index 0000000000000..62d6c9956a7eb
--- /dev/null
+++ b/Zend/tests/gh16630.phpt
@@ -0,0 +1,19 @@
+--TEST--
+GH-16630 (UAF in lexer with encoding translation and heredocs)
+--EXTENSIONS--
+mbstring
+--INI--
+zend.multibyte=On
+zend.script_encoding=ISO-8859-1
+internal_encoding=EUC-JP
+--FILE--
+<?php
+$data3 = <<<CODE
+heredoc
+text
+CODE;
+echo $data3;
+?>
+--EXPECT--
+heredoc
+text
diff --git a/Zend/zend_language_scanner.l b/Zend/zend_language_scanner.l
index c3b27cbfc321c..8b46700eba338 100644
--- a/Zend/zend_language_scanner.l
+++ b/Zend/zend_language_scanner.l
@@ -275,7 +275,7 @@ ZEND_API void zend_restore_lexical_state(zend_lex_state *lex_state)
 	CG(zend_lineno) = lex_state->lineno;
 	zend_restore_compiled_filename(lex_state->filename);
 
-	if (SCNG(script_filtered)) {
+	if (SCNG(script_filtered) && SCNG(script_filtered) != lex_state->script_filtered) {
 		efree(SCNG(script_filtered));
 		SCNG(script_filtered) = NULL;
 	}