diff --git a/Base/res/html/misc/custom-properties.html b/Base/res/html/misc/custom-properties.html
index 253a4557de..308f7e9614 100644
--- a/Base/res/html/misc/custom-properties.html
+++ b/Base/res/html/misc/custom-properties.html
@@ -45,6 +45,11 @@
             border: var(--border);
         }
 
+        .test-inside-a-function {
+            --blue: 255;
+            background-color: rgb(255, 0, var(--blue));
+        }
+
         .test-mixed {
             background: var(--background-color) url("background-repeat.png") var(--background-position) no-repeat;
         }
@@ -178,6 +183,18 @@
         This should have a 10px solid orange border
     </div>
 
+    <pre>
+        .test-inside-a-function {
+            --blue: 255;
+            background-color: rgb(255, 0, var(--blue));
+        }
+    </pre>
+
+    <div class="box test-inside-a-function">
+        <pre>.test-inside-a-function</pre>
+        This should be fuchsia
+    </div>
+
     <h2>Mixed var()</h2>
     <pre>
         :root {
diff --git a/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp b/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
index 17f95c4eb0..27bc80156e 100644
--- a/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
+++ b/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
@@ -4962,9 +4962,18 @@ RefPtr<StyleValue> Parser::parse_as_css_value(PropertyID property_id)
 
 Parser::ParseErrorOr<NonnullRefPtr<StyleValue>> Parser::parse_css_value(PropertyID property_id, TokenStream<ComponentValue>& tokens)
 {
-    auto block_contains_var_or_attr = [](Block const& block, auto&& recurse) -> bool {
+    auto function_contains_var_or_attr = [](Function const& function, auto&& recurse) -> bool {
+        if (function.name().equals_ignoring_case("var"sv) || function.name().equals_ignoring_case("attr"sv))
+            return true;
+        for (auto const& token : function.values()) {
+            if (token.is_function() && recurse(token.function(), recurse))
+                return true;
+        }
+        return false;
+    };
+    auto block_contains_var_or_attr = [function_contains_var_or_attr](Block const& block, auto&& recurse) -> bool {
         for (auto const& token : block.values()) {
-            if (token.is_function() && (token.function().name().equals_ignoring_case("var"sv) || token.function().name().equals_ignoring_case("attr"sv)))
+            if (token.is_function() && function_contains_var_or_attr(token.function(), function_contains_var_or_attr))
                 return true;
             if (token.is_block() && recurse(token.block(), recurse))
                 return true;
@@ -4993,7 +5002,7 @@ Parser::ParseErrorOr<NonnullRefPtr<StyleValue>> Parser::parse_css_value(Property
         }
 
         if (!contains_var_or_attr) {
-            if (token.is_function() && (token.function().name().equals_ignoring_case("var"sv) || token.function().name().equals_ignoring_case("attr"sv)))
+            if (token.is_function() && function_contains_var_or_attr(token.function(), function_contains_var_or_attr))
                 contains_var_or_attr = true;
             else if (token.is_block() && block_contains_var_or_attr(token.block(), block_contains_var_or_attr))
                 contains_var_or_attr = true;