diff --git a/lib/committee/request_unpacker.rb b/lib/committee/request_unpacker.rb
index bbb4337b..25ffea6b 100644
--- a/lib/committee/request_unpacker.rb
+++ b/lib/committee/request_unpacker.rb
@@ -78,11 +78,12 @@ def parse_json(request)
       return nil if request.request_method == "GET" && !@allow_get_body
 
       return nil if request.body.nil?
+      rewind_body(request.body)
       body = request.body.read
       # if request body is empty, we just have empty params
       return nil if body.length == 0
 
-      request.body.rewind
+      rewind_body(request.body)
       hash = JSON.parse(body)
       # We want a hash specifically. '42', 42, and [42] will all be
       # decoded properly, but we can't use them here.
@@ -91,5 +92,9 @@ def parse_json(request)
       end
       self.class.indifferent_params(hash)
     end
+
+    def rewind_body(body)
+      body.rewind if body.respond_to?(:rewind)
+    end
   end
 end
diff --git a/test/request_unpacker_test.rb b/test/request_unpacker_test.rb
index a70862d5..71c3761d 100644
--- a/test/request_unpacker_test.rb
+++ b/test/request_unpacker_test.rb
@@ -10,6 +10,14 @@
     assert_equal([{ "x" => "y" }, false], unpacker.unpack_request_params(request))
   end
 
+  it "unpacks JSON on Content-Type: application/json if the body was not rewound first" do
+    env = { "CONTENT_TYPE" => "application/json", "rack.input" => StringIO.new('{"x":"y"}'), }
+    request = Rack::Request.new(env)
+    request.body.read
+    unpacker = Committee::RequestUnpacker.new
+    assert_equal([{ "x" => "y" }, false], unpacker.unpack_request_params(request))
+  end
+
   it "unpacks JSON on Content-Type: application/vnd.api+json" do
     env = { "CONTENT_TYPE" => "application/vnd.api+json", "rack.input" => StringIO.new('{"x":"y"}'), }
     request = Rack::Request.new(env)