diff --git a/lib/src/client/http2_connection.dart b/lib/src/client/http2_connection.dart
index d0a50b4b..ce87d6ab 100644
--- a/lib/src/client/http2_connection.dart
+++ b/lib/src/client/http2_connection.dart
@@ -161,8 +161,9 @@ class Http2ClientConnection implements connection.ClientConnection {
       metadata,
       compressionCodec,
       userAgent: options.userAgent,
-      grpcAcceptEncodings: callOptions?.metadata['grpc-accept-encoding'] ??
-          options.codecRegistry?.supportedEncodings,
+      grpcAcceptEncodings:
+          (callOptions?.metadata ?? const {})['grpc-accept-encoding'] ??
+              options.codecRegistry?.supportedEncodings,
     );
     final stream = _transportConnection.makeRequest(headers);
     return Http2TransportStream(