diff --git a/lib/Dancer/Handler.pm b/lib/Dancer/Handler.pm
index 0f5e6afe3..eaa586bb5 100644
--- a/lib/Dancer/Handler.pm
+++ b/lib/Dancer/Handler.pm
@@ -62,8 +62,11 @@ sub handle_request {
     Dancer::SharedData->request($request);
 
     # deserialize the request body if possible
-    $request = Dancer::Serializer->process_request($request)
-      if Dancer::App->current->setting('serializer');
+    if (Dancer::App->current->setting('serializer')) {
+        $request = Dancer::Serializer->process_request($request);
+        return $self->render_response unless $request;
+    }
+
 
     # read cookies from client
 
diff --git a/lib/Dancer/Request.pm b/lib/Dancer/Request.pm
index c6b58eb39..0b9bc2976 100644
--- a/lib/Dancer/Request.pm
+++ b/lib/Dancer/Request.pm
@@ -431,7 +431,8 @@ sub _build_params {
         %$previous,                %{$self->{_query_params}},
         %{$self->{_route_params}}, %{$self->{_body_params}},
     };
-
+    # there may be new parameters in need of _decode()ing
+    $self->{_params_are_decoded} = 0;
 }
 
 # Written from PSGI specs:
diff --git a/lib/Dancer/Serializer.pm b/lib/Dancer/Serializer.pm
index 772e52623..cbb46ca0c 100644
--- a/lib/Dancer/Serializer.pm
+++ b/lib/Dancer/Serializer.pm
@@ -91,16 +91,21 @@ sub process_request {
 
     my $old_params = $request->params('body');
 
-    # try to deserialize
+    # deserialize
     my $new_params;
     eval {
         $new_params = engine->deserialize($request->body)
     };
     if ($@) {
+        Dancer::Error->new(
+          code      => 400,
+          title     => "Bad request",
+          message   => "Deserialization failed",
+        )->render;
         Dancer::Logger::core "Unable to deserialize request body with "
           . engine()
           . " : \n$@";
-        return $request;
+        return;
     }
 
     if(!ref $new_params or ref $new_params ne 'HASH'){
diff --git a/t/02_request/19_decode_added_params.t b/t/02_request/19_decode_added_params.t
new file mode 100644
index 000000000..6c2b6d686
--- /dev/null
+++ b/t/02_request/19_decode_added_params.t
@@ -0,0 +1,50 @@
+use Dancer ':tests';
+use Dancer::Test;
+use Test::More;
+use Dancer::ModuleLoader;
+use LWP::UserAgent;
+
+plan skip_all => "skip test with Test::TCP in win32" if  $^O eq 'MSWin32';
+plan skip_all => 'Test::TCP is needed to run this test'
+    unless Dancer::ModuleLoader->load('Test::TCP' => "1.30");
+
+plan skip_all => 'JSON is needed to run this test'
+    unless Dancer::ModuleLoader->load('JSON');
+
+plan tests => 2;
+
+my $unicode = "\x{30dc}\x{a9}";
+
+Test::TCP::test_tcp(
+    client => sub {
+        my $port    = shift;
+        my $ua      = LWP::UserAgent->new;
+        my $request = HTTP::Request->new(
+            POST => "http://127.0.0.1:$port/foo/$unicode",
+            [
+                Host         => 'localhost',
+                Content_Type => 'application/json',
+            ],
+            to_json({ foo => 'bar' }),
+        );
+        my $res = $ua->request($request);
+        ok $res->is_success, 'Successful response from server';
+        is $res->content, 1, 'Correct content';
+    },
+    server => sub {
+        my $port = shift;
+        use Dancer ':tests';
+        set(
+            apphandler   => 'Standalone',
+            port         => $port,
+            show_errors  => 0,
+            startup_info => 0,
+            charset      => 'utf-8',
+            serializer   => 'JSON',
+        );
+        post '/foo/*' => sub {
+            params->{splat}[0] eq $unicode;
+        };
+        Dancer->dance;
+    },
+);
diff --git a/t/14_serializer/02_request_json.t b/t/14_serializer/02_request_json.t
index 9f415708d..979de0ce4 100644
--- a/t/14_serializer/02_request_json.t
+++ b/t/14_serializer/02_request_json.t
@@ -14,13 +14,13 @@ BEGIN {
 set 'serializer' => 'JSON', 'show_errors' => 1;
 
 get  '/'          => sub { { foo => 'bar' } };
-post '/'          => sub { params };
+post '/'          => sub { scalar params };
 put  '/'          => sub { param("id") };
 get  '/error'     => sub { send_error( { foo => 42 }, 401 ) };
 get  '/error_bis' => sub { send_error( 42, 402 ) };
 get  '/json'      => sub {
     content_type('application/json');
-    to_json( { foo => 'bar' } )
+    +{ foo => 'bar' };
 };
 
 response_content_is [ PUT => '/',
@@ -41,8 +41,8 @@ my $res = dancer_response
   (
    POST => '/',
    {
-    params  => { foo            => 1 },
-    headers => [ 'Content-Type' => 'application/json' ]
+    headers => [ 'Content-Type' => 'application/json' ],
+    body    => to_json({ foo => 1 }),
    }
   );
 
diff --git a/t/14_serializer/04_request_xml.t b/t/14_serializer/04_request_xml.t
index 3302a2be9..d9fdd7690 100644
--- a/t/14_serializer/04_request_xml.t
+++ b/t/14_serializer/04_request_xml.t
@@ -34,8 +34,8 @@ SKIP: {
     my $res = dancer_response(
         POST => '/',
         {
-            params  => { foo            => 1 },
-            headers => [ 'Content-Type' => 'text/xml' ]
+            headers => [ 'Content-Type' => 'text/xml' ],
+            body    => to_xml({ foo => 1 }),
         }
     );
     is_deeply(
diff --git a/t/14_serializer/19_deserialization_failure.t b/t/14_serializer/19_deserialization_failure.t
new file mode 100644
index 000000000..7de051e71
--- /dev/null
+++ b/t/14_serializer/19_deserialization_failure.t
@@ -0,0 +1,81 @@
+use Dancer ':tests';
+use Dancer::Test;
+use Test::More;
+use Dancer::ModuleLoader;
+use LWP::UserAgent;
+
+plan skip_all => "skip test with Test::TCP in win32" if  $^O eq 'MSWin32';
+plan skip_all => 'Test::TCP is needed to run this test'
+    unless Dancer::ModuleLoader->load('Test::TCP' => "1.30");
+
+plan skip_all => 'JSON is needed to run this test'
+    unless Dancer::ModuleLoader->load('JSON');
+
+plan tests => 3;
+
+set serializer => 'JSON';
+
+my $data = { foo => 'bar' };
+
+Test::TCP::test_tcp(
+    client => sub {
+        my $port    = shift;
+        my $ua      = LWP::UserAgent->new;
+        my $request = HTTP::Request->new(
+            PUT => "http://127.0.0.1:$port/deserialization",
+            [
+                Host         => 'localhost',
+                Content_Type => 'application/json'
+            ],
+            to_json($data),
+        );
+        my $res = $ua->request($request);
+        ok $res->is_success, 'Successful response from server';
+        is_deeply from_json($res->content), $data, 'Correct content';
+    },
+    server => sub {
+        my $port = shift;
+        use Dancer ':tests';
+        set(
+            apphandler   => 'Standalone',
+            port         => $port,
+            show_errors  => 0,
+            startup_info => 0,
+        );
+        put '/deserialization' => sub { $data };
+        Dancer->dance;
+    },
+);
+
+Test::TCP::test_tcp(
+    client => sub {
+        my $port    = shift;
+        my $ua      = LWP::UserAgent->new;
+        my $request = HTTP::Request->new(
+            PUT => "http://127.0.0.1:$port/deserialization",
+            [
+                Host         => 'localhost',
+                Content_Type => 'application/json'
+            ],
+            # broken JSON
+            '{ "foo": "bar", }',
+        );
+        my $res = $ua->request($request);
+        is $res->code, 400, '400 bad request';
+    },
+    server => sub {
+        my $port = shift;
+        use Dancer ':tests';
+        set(
+            apphandler   => 'Standalone',
+            port         => $port,
+            show_errors  => 1,
+            startup_info => 0,
+        );
+        put '/deserialization' => sub { $data };
+        Dancer->dance;
+    },
+);
+
+
+