diff --git a/Libraries/LibWeb/CSS/Parser/RuleParsing.cpp b/Libraries/LibWeb/CSS/Parser/RuleParsing.cpp
index d0be36eea6d..5f0a84da3d9 100644
--- a/Libraries/LibWeb/CSS/Parser/RuleParsing.cpp
+++ b/Libraries/LibWeb/CSS/Parser/RuleParsing.cpp
@@ -196,7 +196,7 @@ GC::Ptr<CSSImportRule> Parser::convert_to_import_rule(AtRule const& rule)
         return {};
     }
 
-    if (!rule.child_rules_and_lists_of_declarations.is_empty()) {
+    if (rule.is_block_rule) {
         dbgln_if(CSS_PARSER_DEBUG, "Failed to parse @import rule: Block is not allowed.");
         return {};
     }
@@ -470,7 +470,7 @@ GC::Ptr<CSSNamespaceRule> Parser::convert_to_namespace_rule(AtRule const& rule)
         return {};
     }
 
-    if (!rule.child_rules_and_lists_of_declarations.is_empty()) {
+    if (rule.is_block_rule) {
         dbgln_if(CSS_PARSER_DEBUG, "Failed to parse @namespace rule: Block is not allowed.");
         return {};
     }
diff --git a/Tests/LibWeb/Ref/expected/wpt-import/css/css-namespaces/reference/ref-lime-5.xml b/Tests/LibWeb/Ref/expected/wpt-import/css/css-namespaces/reference/ref-lime-5.xml
new file mode 100644
index 00000000000..9c45f9de7cb
--- /dev/null
+++ b/Tests/LibWeb/Ref/expected/wpt-import/css/css-namespaces/reference/ref-lime-5.xml
@@ -0,0 +1,14 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+ <head>
+  <link rel="author" title="L. David Baron" href="https://dbaron.org/"/>
+  <link rel="author" title="Mozilla" href="http://mozilla.org/"/>
+  <title>CSS Namespaces Test Suite reference</title>
+ </head>
+ <body>
+  <p><test style="background: lime">This sentence should have a green background.</test></p>
+  <p><test style="background: lime">This sentence should have a green background.</test></p>
+  <p><test style="background: lime">This sentence should have a green background.</test></p>
+  <p><test style="background: lime">This sentence should have a green background.</test></p>
+  <p><test style="background: lime">This sentence should have a green background.</test></p>
+ </body>
+</html>
diff --git a/Tests/LibWeb/Ref/input/wpt-import/css/css-namespaces/syntax-013.xml b/Tests/LibWeb/Ref/input/wpt-import/css/css-namespaces/syntax-013.xml
new file mode 100644
index 00000000000..5ec8d84b7c0
--- /dev/null
+++ b/Tests/LibWeb/Ref/input/wpt-import/css/css-namespaces/syntax-013.xml
@@ -0,0 +1,44 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+ <head>
+  <link rel="author" title="Anne van Kesteren" href="http://annevankesteren.nl/"/>
+  <link rel="author" title="Opera Software ASA" href="http://opera.com/"/>
+  <link rel="author" title="Elika J. Etemad" href="http://fantasai.inkedblade.net/contact"/>
+  <link rel="help" href="http://www.w3.org/TR/css-namespaces-3/#syntax"/>
+  <link rel="match" href="../../../../expected/wpt-import/css/css-namespaces/reference/ref-lime-5.xml"/>
+  <meta name="flags" content="invalid"/>
+  <title>CSS Namespaces Test Suite: @namespace error handling</title>
+  <style>
+   t, t2, t3, t4, t5 { background:red }
+  </style>
+  <style>
+   @namespace "test" {}
+   t { background:lime }
+  </style>
+  <style id="a">@namespace x "test</style>
+  <script>
+   document.getElementById("a").sheet.insertRule("x|t2 {background:lime }", 1)
+  </script>
+  <style>
+   @namespace "fail;
+   ; t3 { background:lime }
+  </style>
+  <style>
+   @namespace url('fail);
+     t4 { background:red !important; }
+   );
+   t4 { background:lime }
+  </style>
+  <style>
+   @namespace url(test);
+   @namespace url('test' x);
+   t5 { background:lime }
+  </style>
+ </head>
+ <body>
+  <p><t>This sentence should have a green background.</t></p>
+  <p><t2 xmlns="test">This sentence should have a green background.</t2></p>
+  <p><t3>This sentence should have a green background.</t3></p>
+  <p><t4>This sentence should have a green background.</t4></p>
+  <p><t5 xmlns="test">This sentence should have a green background.</t5></p>
+ </body>
+</html>
