diff --git a/src/a2a/server/request_handlers/grpc_handler.py b/src/a2a/server/request_handlers/grpc_handler.py
index e2ec69a15..20774001c 100644
--- a/src/a2a/server/request_handlers/grpc_handler.py
+++ b/src/a2a/server/request_handlers/grpc_handler.py
@@ -3,7 +3,7 @@
 import logging
 
 from abc import ABC, abstractmethod
-from collections.abc import AsyncIterable, Sequence
+from collections.abc import AsyncIterable
 
 
 try:
@@ -53,13 +53,11 @@ def build(self, context: grpc.aio.ServicerContext) -> ServerCallContext:
 def _get_metadata_value(
     context: grpc.aio.ServicerContext, key: str
 ) -> list[str]:
-    md = context.invocation_metadata
-    raw_values: list[str | bytes] = []
-    if isinstance(md, Metadata):
-        raw_values = md.get_all(key)
-    elif isinstance(md, Sequence):
-        lower_key = key.lower()
-        raw_values = [e for (k, e) in md if k.lower() == lower_key]
+    md = context.invocation_metadata()
+    raw_values: list[str | bytes] = (
+        md.get_all(key) if isinstance(md, Metadata) else []
+    )
+
     return [e if isinstance(e, str) else e.decode('utf-8') for e in raw_values]
 
 
diff --git a/tests/server/request_handlers/test_grpc_handler.py b/tests/server/request_handlers/test_grpc_handler.py
index 26f923c14..5c7e26ef1 100644
--- a/tests/server/request_handlers/test_grpc_handler.py
+++ b/tests/server/request_handlers/test_grpc_handler.py
@@ -321,7 +321,7 @@ async def test_send_message_with_extensions(
         mock_request_handler: AsyncMock,
         mock_grpc_context: AsyncMock,
     ) -> None:
-        mock_grpc_context.invocation_metadata = grpc.aio.Metadata(
+        mock_grpc_context.invocation_metadata.return_value = grpc.aio.Metadata(
             (HTTP_EXTENSION_HEADER, 'foo'),
             (HTTP_EXTENSION_HEADER, 'bar'),
         )
@@ -361,7 +361,7 @@ async def test_send_message_with_comma_separated_extensions(
         mock_request_handler: AsyncMock,
         mock_grpc_context: AsyncMock,
     ) -> None:
-        mock_grpc_context.invocation_metadata = grpc.aio.Metadata(
+        mock_grpc_context.invocation_metadata.return_value = grpc.aio.Metadata(
             (HTTP_EXTENSION_HEADER, 'foo ,, bar,'),
             (HTTP_EXTENSION_HEADER, 'baz  , bar'),
         )
@@ -386,7 +386,7 @@ async def test_send_streaming_message_with_extensions(
         mock_request_handler: AsyncMock,
         mock_grpc_context: AsyncMock,
     ) -> None:
-        mock_grpc_context.invocation_metadata = grpc.aio.Metadata(
+        mock_grpc_context.invocation_metadata.return_value = grpc.aio.Metadata(
             (HTTP_EXTENSION_HEADER, 'foo'),
             (HTTP_EXTENSION_HEADER, 'bar'),
         )