diff --git a/ext/dom/document.c b/ext/dom/document.c
index 22bb90d5d88db..0e15e7a110652 100644
--- a/ext/dom/document.c
+++ b/ext/dom/document.c
@@ -2024,7 +2024,6 @@ static void dom_load_html(INTERNAL_FUNCTION_PARAMETERS, int mode) /* {{{ */
 		}
 		ctxt = htmlCreateFileParserCtxt(source, NULL);
 	} else {
-		source_len = xmlStrlen((xmlChar *) source);
 		if (ZEND_SIZE_T_INT_OVFL(source_len)) {
 			php_error_docref(NULL, E_WARNING, "Input string is too long");
 			RETURN_FALSE;
diff --git a/ext/dom/tests/bug80268.phpt b/ext/dom/tests/bug80268.phpt
new file mode 100644
index 0000000000000..0fe50b85e8611
--- /dev/null
+++ b/ext/dom/tests/bug80268.phpt
@@ -0,0 +1,24 @@
+--TEST--
+Bug #80268 (loadHTML() truncates at NUL bytes)
+--SKIPIF--
+<?php require_once('skipif.inc'); ?>
+--FILE--
+<?php
+$doc = new DOMDocument;
+$doc->loadHTML("<p>foo\0bar</p>");
+$html = $doc->saveHTML();
+var_dump(strpos($html, '<p>foo</p>') !== false);
+
+file_put_contents(__DIR__ . '/80268.html', "<p>foo\0bar</p>");
+$doc = new DOMDocument;
+$doc->loadHTMLFile(__DIR__ . '/80268.html');
+$html = $doc->saveHTML();
+var_dump(strpos($html, '<p>foo</p>') !== false);
+?>
+--CLEAN--
+<?php
+unlink(__DIR__ . '/80268.html');
+?>
+--EXPECT--
+bool(true)
+bool(true)