diff --git a/Libraries/LibWeb/CSS/Parser/Parser.cpp b/Libraries/LibWeb/CSS/Parser/Parser.cpp
index cf1e4e8593b..f5a29c88aa8 100644
--- a/Libraries/LibWeb/CSS/Parser/Parser.cpp
+++ b/Libraries/LibWeb/CSS/Parser/Parser.cpp
@@ -291,7 +291,7 @@ OwnPtr<BooleanExpression> Parser::parse_supports_feature(TokenStream<ComponentVa
     if (first_token.is_block() && first_token.block().is_paren()) {
         TokenStream block_tokens { first_token.block().value };
         // FIXME: Parsing and then converting back to a string is weird.
-        if (auto declaration = consume_a_declaration(block_tokens); declaration.has_value()) {
+        if (auto declaration = consume_a_declaration(block_tokens); declaration.has_value() && !block_tokens.has_next_token()) {
             transaction.commit();
             auto supports_declaration = Supports::Declaration::create(
                 declaration->to_string(),
diff --git a/Tests/LibWeb/Ref/expected/wpt-import/css/css-conditional/at-supports-038.html b/Tests/LibWeb/Ref/expected/wpt-import/css/css-conditional/at-supports-038.html
new file mode 100644
index 00000000000..8ff3f2fccf5
--- /dev/null
+++ b/Tests/LibWeb/Ref/expected/wpt-import/css/css-conditional/at-supports-038.html
@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<html>
+    <style>
+        div {
+            width: 100px;
+            height: 100px;
+            background-color: green;
+        }
+    </style>
+    <p>
+        Test passes if there is a <strong>filled green square</strong> and <strong>no red</strong>.
+    </p>
+    <div></div>
+</html>
diff --git a/Tests/LibWeb/Ref/expected/wpt-import/css/css-conditional/at-supports-039.html b/Tests/LibWeb/Ref/expected/wpt-import/css/css-conditional/at-supports-039.html
new file mode 100644
index 00000000000..8ff3f2fccf5
--- /dev/null
+++ b/Tests/LibWeb/Ref/expected/wpt-import/css/css-conditional/at-supports-039.html
@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<html>
+    <style>
+        div {
+            width: 100px;
+            height: 100px;
+            background-color: green;
+        }
+    </style>
+    <p>
+        Test passes if there is a <strong>filled green square</strong> and <strong>no red</strong>.
+    </p>
+    <div></div>
+</html>
diff --git a/Tests/LibWeb/Ref/input/wpt-import/css/css-conditional/at-supports-038.html b/Tests/LibWeb/Ref/input/wpt-import/css/css-conditional/at-supports-038.html
new file mode 100644
index 00000000000..32b9a6f8a91
--- /dev/null
+++ b/Tests/LibWeb/Ref/input/wpt-import/css/css-conditional/at-supports-038.html
@@ -0,0 +1,42 @@
+<!DOCTYPE html>
+<html>
+	<head>
+		<meta charset="utf-8">
+		<title>CSS Test (Conditional Rules): a supports condition declaration can not end with a semi-colon</title>
+		<link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
+		<link rel="help" href="http://www.w3.org/TR/css3-conditional/#at-supports" title="6. Feature queries: the '@supports' rule">
+		<link rel="match" href="../../../../expected/wpt-import/css/css-conditional/at-supports-001-ref.html">
+		<meta name="flags" content="invalid">
+		<meta name="assert" content="Each individual single supports condition declaration can not end up with a semi-colon ';'. A semi-colon is a punctuation separator of multiple CSS declarations and thus is not part of an individual CSS declaration per se.">
+
+    <!--
+
+    supports_condition_in_parens
+      : ( '(' S* supports_condition ')' S* ) | supports_declaration_condition |
+        general_enclosed
+      ;
+
+    -->
+
+		<style>
+			div
+			{
+				background-color: red;
+				height: 100px;
+				width: 100px;
+			}
+
+			@supports (margin: 0;) { div {background-color: red !important;} }
+
+			@supports (margin: 0) { div {background-color: green;} }
+		</style>
+	</head>
+
+	<body>
+
+		<p>Test passes if there is a <strong>filled green square</strong> and <strong>no red</strong>.</p>
+
+		<div></div>
+
+	</body>
+</html>
diff --git a/Tests/LibWeb/Ref/input/wpt-import/css/css-conditional/at-supports-039.html b/Tests/LibWeb/Ref/input/wpt-import/css/css-conditional/at-supports-039.html
new file mode 100644
index 00000000000..c8f55a9b48b
--- /dev/null
+++ b/Tests/LibWeb/Ref/input/wpt-import/css/css-conditional/at-supports-039.html
@@ -0,0 +1,42 @@
+<!DOCTYPE html>
+<html>
+	<head>
+		<meta charset="utf-8">
+		<title>CSS Test (Conditional Rules): a supports condition declaration can not end with a semi-colon</title>
+		<link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
+		<link rel="help" href="http://www.w3.org/TR/css3-conditional/#at-supports" title="6. Feature queries: the '@supports' rule">
+		<link rel="match" href="../../../../expected/wpt-import/css/css-conditional/at-supports-001-ref.html">
+		<meta name="flags" content="invalid">
+		<meta name="assert" content="Each individual single supports condition declaration can not end up with a semi-colon ';'. A semi-colon is a punctuation separator of multiple CSS declarations and thus is not part of an individual CSS declaration per se.">
+
+    <!--
+
+    supports_condition_in_parens
+      : ( '(' S* supports_condition ')' S* ) | supports_declaration_condition |
+        general_enclosed
+      ;
+
+    -->
+
+		<style>
+			div
+			{
+				background-color: red;
+				height: 100px;
+				width: 100px;
+			}
+
+			@supports (margin: 0) { div {background-color: green;} }
+
+			@supports (margin: 0;) { div {background-color: red;}	}
+		</style>
+	</head>
+
+	<body>
+
+		<p>Test passes if there is a <strong>filled green square</strong> and <strong>no red</strong>.</p>
+
+		<div></div>
+
+	</body>
+</html>
