diff --git a/lib/mcp/server/transports/stdio_transport.rb b/lib/mcp/server/transports/stdio_transport.rb
index 8c758124..37d33fb3 100644
--- a/lib/mcp/server/transports/stdio_transport.rb
+++ b/lib/mcp/server/transports/stdio_transport.rb
@@ -168,7 +168,9 @@ def parse_line(line)
         # (an `initialize` after a modern lock, a modern envelope after a legacy lock, or a missing envelope after a modern lock)
         # are rejected in-band by `Server#lift_request_envelope`.
         def dispatch_with_era(parsed)
-          response = @session.handle(parsed)
+          # Passing `auth_info:` keeps Ruby 2.7 from taking the request Hash as keyword arguments,
+          # which works but warns that the conversion is deprecated.
+          response = @session.handle(parsed, auth_info: nil)
           lock_modern_era_on_success(parsed, response)
           response
         end
diff --git a/test/mcp/server/transports/stdio_transport_test.rb b/test/mcp/server/transports/stdio_transport_test.rb
index 683e2ae4..73ed1894 100644
--- a/test/mcp/server/transports/stdio_transport_test.rb
+++ b/test/mcp/server/transports/stdio_transport_test.rb
@@ -135,6 +135,25 @@ class StdioTransportTest < ActiveSupport::TestCase
           end
         end
 
+        test "open passes a request to the session without a keyword argument warning" do
+          request = { jsonrpc: "2.0", method: "ping", id: "1" }
+          input = StringIO.new(JSON.generate(request) + "\n")
+          original_stdin = $stdin
+          original_deprecated = Warning[:deprecated]
+
+          begin
+            $stdin = input
+            Warning[:deprecated] = true
+
+            _out, err = capture_io { @transport.open }
+
+            assert_empty(err)
+          ensure
+            $stdin = original_stdin
+            Warning[:deprecated] = original_deprecated
+          end
+        end
+
         test "open handles a malformed JSON-RPC batch element and emits an error response" do
           input = StringIO.new("[[]]\n")
           output = StringIO.new