diff --git a/Libraries/LibWeb/CSS/SelectorEngine.cpp b/Libraries/LibWeb/CSS/SelectorEngine.cpp
index b11887ba98a..cdc7a5ea3f2 100644
--- a/Libraries/LibWeb/CSS/SelectorEngine.cpp
+++ b/Libraries/LibWeb/CSS/SelectorEngine.cpp
@@ -68,11 +68,15 @@ static inline bool matches_lang_pseudo_class(DOM::Element const& element, Vector
continue;
if (language == "*"sv)
return true;
- if (!element_language.contains('-') && Infra::is_ascii_case_insensitive_match(element_language, language))
- return true;
- auto parts = element_language.split_limit('-', 2).release_value_but_fixme_should_propagate_errors();
- if (!parts.is_empty() && Infra::is_ascii_case_insensitive_match(parts[0], language))
- return true;
+ auto element_language_length = element_language.bytes_as_string_view().length();
+ auto language_length = language.bytes_as_string_view().length();
+ if (element_language_length == language_length) {
+ if (Infra::is_ascii_case_insensitive_match(element_language, language))
+ return true;
+ } else if (element_language_length > language_length) {
+ if (element_language.starts_with_bytes(language, CaseSensitivity::CaseInsensitive) && element_language.bytes_as_string_view()[language_length] == '-')
+ return true;
+ }
}
return false;
}
diff --git a/Tests/LibWeb/Ref/expected/wpt-import/css/CSS2/selector/lang-pseudoclass-001-ref.html b/Tests/LibWeb/Ref/expected/wpt-import/css/CSS2/selector/lang-pseudoclass-001-ref.html
new file mode 100644
index 00000000000..ac83e80d955
--- /dev/null
+++ b/Tests/LibWeb/Ref/expected/wpt-import/css/CSS2/selector/lang-pseudoclass-001-ref.html
@@ -0,0 +1,24 @@
+
+
+CSS Reference
+
+
+ This line should be green
+ This line should be green
+ This line should be green
+ This line should be green
+ This line should be green
+
+ This line should be green and this should be green too
+ This line should be green
This line should NOT be green
This line should NOT be green but this should be green
+
+ This line should NOT be green
+ This line should NOT be green
+ This line should NOT be green
+
diff --git a/Tests/LibWeb/Ref/input/wpt-import/css/CSS2/selector/lang-pseudoclass-001.html b/Tests/LibWeb/Ref/input/wpt-import/css/CSS2/selector/lang-pseudoclass-001.html
new file mode 100644
index 00000000000..defddc2cbe7
--- /dev/null
+++ b/Tests/LibWeb/Ref/input/wpt-import/css/CSS2/selector/lang-pseudoclass-001.html
@@ -0,0 +1,36 @@
+
+
+
+ CSS Test: :lang pseudoclass
+
+
+
+
+
+
+
+
+
+
+ This line should be green
+ This line should be green
+ This line should be green
+
+ This line should be green
+ This line should be green
+
+ This line should be green and this should be green too
+ This line should be green
This line should NOT be green
This line should NOT be green but this should be green
+
+ This line should NOT be green
+ This line should NOT be green
+ This line should NOT be green
+
+
diff --git a/Tests/LibWeb/Ref/input/wpt-import/css/CSS2/selector/lang-pseudoclass-002.xht b/Tests/LibWeb/Ref/input/wpt-import/css/CSS2/selector/lang-pseudoclass-002.xht
new file mode 100644
index 00000000000..be18d797198
--- /dev/null
+++ b/Tests/LibWeb/Ref/input/wpt-import/css/CSS2/selector/lang-pseudoclass-002.xht
@@ -0,0 +1,40 @@
+
+
+
+ CSS Test: :lang pseudoclass
+
+
+
+
+
+
+
+
+
+
+ This line should be green
+ This line should be green
+ This line should be green
+
+ This line should be green
+ This line should be green
+
+ This line should be green and this should be green too
+
+ This line should be green
This line should NOT be green
This line should NOT be green but this should be green
+
+ This line should NOT be green
+ This line should NOT be green
+ This line should NOT be green
+
+
+
+
+