diff --git a/lib/stitches/valid_mime_type.rb b/lib/stitches/valid_mime_type.rb
index d79aa66..03ca04d 100644
--- a/lib/stitches/valid_mime_type.rb
+++ b/lib/stitches/valid_mime_type.rb
@@ -1,19 +1,26 @@
 require_relative 'allowlist_middleware'
 module Stitches
-  # A middleware that requires all API calls to be for versioned JSON.  This means that the Accept
-  # header (available to Rack apps as HTTP_ACCEPT) should be like so:
+  # A middleware that requires all API calls to be for versioned JSON or Protobuf.
+  #
+  # This means that the Accept header (available to Rack apps as HTTP_ACCEPT) should be like so:
   #
   #     application/json; version=1
   #
   # This just checks that you've specified some numeric version.  ApiVersionConstraint should be used
   # to "lock down" the versions you accept.
+  # 
+  # Or in the case of a protobuf encoded payload the header should be like so:
+  #
+  #     application/protobuf
+  #
+  # There isn't an accepted standard for protobuf encoded payloads but this form is common.
   class ValidMimeType < Stitches::AllowlistMiddleware
 
   protected
 
     def do_call(env)
       accept = String(env["HTTP_ACCEPT"])
-      if accept =~ %r{application/json} && accept =~ %r{version=\d+}
+      if (accept =~ %r{application/json} && accept =~ %r{version=\d+}) || accept =~ %r{application/protobuf}
         @app.call(env)
       else
         not_acceptable_response(accept)
@@ -24,7 +31,7 @@ def do_call(env)
 
     def not_acceptable_response(accept_header)
       status = 406
-      body = "Not Acceptable - '#{accept_header}' didn't have the right mime type or version number. We only accept application/json with a version"
+      body = "Not Acceptable - '#{accept_header}' didn't have the right mime type or version number. We only accept application/json with a version or application/protobuf"
       header = { "WWW-Authenticate" => accept_header }
       Rack::Response.new(body, status, header).finish
     end
diff --git a/spec/valid_mime_type_spec.rb b/spec/valid_mime_type_spec.rb
index e8fd953..9f177ab 100644
--- a/spec/valid_mime_type_spec.rb
+++ b/spec/valid_mime_type_spec.rb
@@ -132,6 +132,22 @@
       end
     end
 
+    context "protbuf mime type" do
+      let(:env) {
+        {
+          "PATH_INFO" => "/api/ping",
+          "HTTP_ACCEPT" => "application/protobuf",
+        }
+      }
+
+      before do
+        @response = middleware.call(env)
+      end
+      it "calls through to the rest of the chain" do
+        expect(app).to have_received(:call).with(env)
+      end
+    end
+
     context "unacceptable responses" do
       before do
         @response = middleware.call(env)