diff --git a/NEWS b/NEWS
index 994cf589245..2e73298dc27 100644
--- a/NEWS
+++ b/NEWS
@@ -13,6 +13,9 @@ PHP                                                                        NEWS
 - COM:
   . Fixed bug #62474 (com_event_sink crashes on certain arguments). (cmb)
 
+- DOM:
+  . Fixed bug #80268 (loadHTML() truncates at NUL bytes). (cmb)
+
 - IMAP:
   . Fixed bug #76618 (segfault on imap_reopen). (girgias)
   . Fixed bug #80239 (imap_rfc822_write_address() leaks memory). (cmb)
diff --git a/ext/dom/document.c b/ext/dom/document.c
index 23bdcae1e0c..c6d0f723f89 100644
--- a/ext/dom/document.c
+++ b/ext/dom/document.c
@@ -1840,7 +1840,6 @@ 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 00000000000..0fe50b85e86
--- /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)