diff --git a/ext/dom/tests/modern/html/encoding/HTMLDocument_createFromFile_http_header.phpt b/ext/dom/tests/modern/html/encoding/HTMLDocument_createFromFile_http_header.phpt
index 3209c3e5d6ae0..130447228f4d8 100644
--- a/ext/dom/tests/modern/html/encoding/HTMLDocument_createFromFile_http_header.phpt
+++ b/ext/dom/tests/modern/html/encoding/HTMLDocument_createFromFile_http_header.phpt
@@ -12,6 +12,10 @@ http_server_skipif();
 require "./ext/standard/tests/http/server.inc";
 
 $tests = [
+    "No slashes" => [
+        "foo",
+        "      ",
+    ],
     "Invalid type/subtype" => [
         "/html; Charset=\"ISO-8859-1\"",
         "text/; Charset=\"ISO-8859-1\"",
@@ -32,6 +36,8 @@ $tests = [
     "All valid inputs" => [
         "text/html; charset=ISO-8859-1",
         "\t\r text/html; charset=ISO-8859-1   \t",
+        "\t\r text/html; charset=ISO-8859-1   \t;bar=\"foo\"",
+        "\t\r text/html; charset=ISO-8859-1   \t;bar=\"foo\"\r\n\t ",
         "text/html; foo=bar;charset=ISO-8859-1",
         "text/html; foo=bar;charset=ISO-8859-1;bar=\"foooooo\"",
         "text/html;;;; charset=ISO-8859-1",
@@ -45,6 +51,7 @@ $tests = [
         "text/html;Charset=\"ISO-8859-1\\",
         "text/html;Charset=\"ISO-8859-1\\\"",
         "text/html;Charset=\"foobar\\\"",
+        "text/html;Charset=\"%7F\\\"",
         "text/html;Charset=\"\\\"",
         "text/html;Charset=",
     ],
@@ -62,6 +69,9 @@ foreach ($tests as $name => $headers) {
 }
 ?>
 --EXPECT--
+--- No slashes ---
+���
+���
 --- Invalid type/subtype ---
 ���
 ���
@@ -88,9 +98,12 @@ foreach ($tests as $name => $headers) {
 äöü
 äöü
 äöü
+äöü
+äöü
 --- Valid input, but invalid encoding name ---
 ���
 ���
 ���
 ���
 ���
+���
diff --git a/ext/libxml/mime_sniff.c b/ext/libxml/mime_sniff.c
index 5692f70ee251e..79ce1dc46b5e0 100644
--- a/ext/libxml/mime_sniff.c
+++ b/ext/libxml/mime_sniff.c
@@ -195,7 +195,7 @@ PHP_LIBXML_API zend_string *php_libxml_sniff_charset_from_string(const char *sta
 	while (start < end && is_http_whitespace(*start)) {
 		start++;
 	}
-	while (start < end && is_http_whitespace(*end)) {
+	while (start < end && is_http_whitespace(*(end - 1))) {
 		end--;
 	}