diff --git a/packages/celest/lib/src/runtime/serve.dart b/packages/celest/lib/src/runtime/serve.dart
index b13e24b4..8b84b29e 100644
--- a/packages/celest/lib/src/runtime/serve.dart
+++ b/packages/celest/lib/src/runtime/serve.dart
@@ -57,14 +57,20 @@ abstract base class CloudFunctionTarget {
     init();
   }
 
+  static const _contextHeaderPrefix = 'X-Celest-Context-';
+  static final _contextHeaderMatcher = RegExp(
+    _contextHeaderPrefix,
+    caseSensitive: false,
+  );
+
   Future<Response> _handler(Request request) async {
     final bodyJson = await request.decodeJson();
-    const contextHeaderPrefix = 'X-Celest-Context-';
     final response = await runZoned(
       () => handle({
         for (final MapEntry(:key, :value) in request.headers.entries)
-          if (key.startsWith(contextHeaderPrefix))
-            key.substring(contextHeaderPrefix.length): value,
+          if (key.startsWith(_contextHeaderMatcher))
+            '\$${key.substring(_contextHeaderPrefix.length).toLowerCase()}':
+                value,
         ...bodyJson,
       }),
       zoneSpecification: ZoneSpecification(