diff --git a/README.md b/README.md
index cd37f63..3c9388b 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,6 @@
 [![Installs](https://img.shields.io/packagist/dt/phpro/api-problem.svg)](https://packagist.org/packages/phpro/api-problem/stats)
 [![Packagist](https://img.shields.io/packagist/v/phpro/api-problem.svg)](https://packagist.org/packages/phpro/api-problem)
 
-
 # Api Problem
 
 This package provides a [RFC7807](https://tools.ietf.org/html/rfc7807) Problem details implementation.
@@ -13,7 +12,6 @@ Since handling the exceptions is up to the framework, here is a list of known fr
 
 - **Symfony** `^4.1`: [ApiProblemBundle](https://www.github.com/phpro/api-problem-bundle)
 
-
 ## Installation
 
 ```sh
@@ -34,14 +32,26 @@ throw new ApiProblemException(
 
 ### Built-in problems
 
-- [ExceptionApiProblem](#exceptionapiproblem)
-- [ForbiddenProblem](#forbiddenproblem)
-- [HttpApiProblem](#httpapiproblem)
-- [NotFoundProblem](#notfoundproblem)
-- [UnauthorizedProblem](#unauthorizedproblem)
-- [ValidationApiProblem](#validationapiproblem)
-- [BadRequestProblem](#badrequestproblem)
-- [ConflictProblem](#conflictproblem)
+- General problems
+  - [ExceptionApiProblem](#exceptionapiproblem)
+  - [HttpApiProblem](#httpapiproblem)
+
+- Symfony integration problems
+  - [ValidationApiProblem](#validationapiproblem)
+
+- Http problems
+  - 400 [BadRequestProblem](#badrequestproblem)
+  - 401 [UnauthorizedProblem](#unauthorizedproblem)
+  - 403 [ForbiddenProblem](#forbiddenproblem)
+  - 404 [NotFoundProblem](#notfoundproblem)
+  - 405 [MethodNotAllowedProblem](#methodnotallowedproblem)
+  - 409 [ConflictProblem](#conflictproblem)
+  - 412 [PreconditionFailedProblem](#preconditionfailedproblem)
+  - 415 [UnsupportedMediaTypeProblem](#unsupportedmediatypeproblem)
+  - 418 [IAmATeapotProblem](#iamateapotproblem)
+  - 422 [UnprocessableEntityProblem](#unprocessableentityproblem)
+  - 423 [LockedProblem](#lockedproblem)
+  - 428 [PreconditionRequiredProblem](#preconditionrequiredproblem)
 
 #### ExceptionApiProblem
 
@@ -90,54 +100,69 @@ new ExceptionApiProblem(new \Exception('message', 500));
 }
 ````
 
-#### ForbiddenProblem
+#### HttpApiProblem
 
 ```php
-use Phpro\ApiProblem\Http\ForbiddenProblem;
+use Phpro\ApiProblem\Http\HttpApiProblem;
 
-new ForbiddenProblem('Not authorized to access gold.');
+new HttpApiProblem(404, ['detail' => 'The book could not be found.']);
 ```
 
 ```json
 {
-  "status": 403,
-  "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
-  "title": "Forbidden",
-  "detail": "Not authorized to access gold."
+    "status": 404,
+    "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
+    "title": "Not found",
+    "detail": "The book could not be found."
 }
 ````
 
-#### HttpApiProblem
+#### ValidationApiProblem
+
+```sh
+composer require symfony/validator:^4.1
+```
 
 ```php
-use Phpro\ApiProblem\Http\HttpApiProblem;
+use Phpro\ApiProblem\Http\ValidationApiProblem;
+use Symfony\Component\Validator\ConstraintViolation;
+use Symfony\Component\Validator\ConstraintViolationList;
 
-new HttpApiProblem(404, ['detail' => 'The book could not be found.']);
+new ValidationApiProblem(new ConstraintViolationList([
+    new ConstraintViolation('Invalid email', '', [], '', 'email', '', null, '8615ecd9-afcb-479a-9c78-8bcfe260cf2a'),
+]));
 ```
 
 ```json
 {
-    "status": 404,
-    "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
-    "title": "Not found",
-    "detail": "The book could not be found."
+    "status": 400,
+    "type": "https:\/\/symfony.com\/errors\/validation",
+    "title": "Validation Failed",
+    "detail": "email: Invalid Email",
+    "violations": [
+        {
+            "propertyPath": "email",
+            "title": "Invalid email",
+            "type": "urn:uuid:8615ecd9-afcb-479a-9c78-8bcfe260cf2a"
+        }
+    ]
 }
 ````
 
-#### NotFoundProblem
+#### BadRequestProblem
 
 ```php
-use Phpro\ApiProblem\Http\NotFoundProblem;
+use Phpro\ApiProblem\Http\BadRequestProblem;
 
-new NotFoundProblem('The book with ID 20 could not be found.');
+new BadRequestProblem('Bad request. Bad!.');
 ```
 
 ```json
 {
-    "status": 404,
+    "status": 400,
     "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
-    "title": "Not found",
-    "detail": "The book with ID 20 could not be found."
+    "title": "Bad Request",
+    "detail": "Bad request. Bad!"
 }
 ````
 
@@ -158,52 +183,54 @@ new UnauthorizedProblem('You are not authorized to access X.');
 }
 ````
 
-#### ValidationApiProblem
+#### ForbiddenProblem
 
-```sh
-composer require symfony/validator:^4.1
+```php
+use Phpro\ApiProblem\Http\ForbiddenProblem;
+
+new ForbiddenProblem('Not authorized to access gold.');
 ```
 
+```json
+{
+  "status": 403,
+  "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
+  "title": "Forbidden",
+  "detail": "Not authorized to access gold."
+}
+````
+
+#### NotFoundProblem
+
 ```php
-use Phpro\ApiProblem\Http\ValidationApiProblem;
-use Symfony\Component\Validator\ConstraintViolation;
-use Symfony\Component\Validator\ConstraintViolationList;
+use Phpro\ApiProblem\Http\NotFoundProblem;
 
-new ValidationApiProblem(new ConstraintViolationList([
-    new ConstraintViolation('Invalid email', '', [], '', 'email', '', null, '8615ecd9-afcb-479a-9c78-8bcfe260cf2a'),
-]));
+new NotFoundProblem('The book with ID 20 could not be found.');
 ```
 
 ```json
 {
-    "status": 400,
-    "type": "https:\/\/symfony.com\/errors\/validation",
-    "title": "Validation Failed",
-    "detail": "email: Invalid Email",
-    "violations": [
-        {
-            "propertyPath": "email",
-            "title": "Invalid email",
-            "type": "urn:uuid:8615ecd9-afcb-479a-9c78-8bcfe260cf2a"
-        }
-    ]
+    "status": 404,
+    "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
+    "title": "Not found",
+    "detail": "The book with ID 20 could not be found."
 }
 ````
 
-#### BadRequestProblem
+#### MethodNotAllowedProblem
 
 ```php
-use Phpro\ApiProblem\Http\BadRequestProblem;
+use Phpro\ApiProblem\Http\MethodNotAllowedProblem;
 
-new BadRequestProblem('Bad request. Bad!.');
+new MethodNotAllowedProblem('Only POST and GET allowed.');
 ```
 
 ```json
 {
-    "status": 400,
+    "status": 405,
     "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
-    "title": "Bad Request",
-    "detail": "Bad request. Bad!"
+    "title": "Method Not Allowed",
+    "detail": "Only POST and GET allowed."
 }
 ````
 
@@ -223,6 +250,108 @@ new ConflictProblem('Duplicated key for book with ID 20.');
 }
 ````
 
+#### PreconditionFailedProblem
+
+```php
+use Phpro\ApiProblem\Http\PreconditionFailedProblem;
+
+new PreconditionFailedProblem('Incorrect entity tag provided.');
+```
+
+```json
+{
+    "status": 412,
+    "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
+    "title": "Precondition Failed",
+    "detail": "Incorrect entity tag provided."
+}
+````
+
+#### UnsupportedMediaTypeProblem
+
+```php
+use Phpro\ApiProblem\Http\UnsupportedMediaTypeProblem;
+
+new UnsupportedMediaTypeProblem('Please provide valid JSON.');
+```
+
+```json
+{
+    "status": 415,
+    "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
+    "title": "Unsupported Media Type",
+    "detail": "Please provide valid JSON."
+}
+````
+
+#### IAmATeapotProblem
+
+```php
+use Phpro\ApiProblem\Http\IAmATeapotProblem;
+
+new IAmATeapotProblem('More tea please.');
+```
+
+```json
+{
+    "status": 418,
+    "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
+    "title": "I'm a teapot",
+    "detail": "More tea please."
+}
+````
+
+#### UnprocessableEntityProblem
+
+```php
+use Phpro\ApiProblem\Http\UnprocessableEntityProblem;
+
+new UnprocessableEntityProblem('Unable to process the contained instructions.');
+```
+
+```json
+{
+    "status": 422,
+    "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
+    "title": "Unprocessable Entity",
+    "detail": "Unable to process the contained instructions."
+}
+````
+
+#### LockedProblem
+
+```php
+use Phpro\ApiProblem\Http\LockedProblem;
+
+new LockedProblem('This door is locked.');
+```
+
+```json
+{
+    "status": 423,
+    "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
+    "title": "Locked",
+    "detail": "This door is locked."
+}
+````
+
+#### PreconditionRequiredProblem
+
+```php
+use Phpro\ApiProblem\Http\PreconditionRequiredProblem;
+
+new PreconditionRequiredProblem('If-match header is required.');
+```
+
+```json
+{
+    "status": 428,
+    "type": "http:\/\/www.w3.org\/Protocols\/rfc2616\/rfc2616-sec10.html",
+    "title": "Precondition Required",
+    "detail": "If-match header is required."
+}
+````
+
 ### Creating your own problem
 
 Creating problem sounds scary right!?
diff --git a/spec/Http/IAmATeapotProblemSpec.php b/spec/Http/IAmATeapotProblemSpec.php
new file mode 100644
index 0000000..99fd4aa
--- /dev/null
+++ b/spec/Http/IAmATeapotProblemSpec.php
@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace spec\Phpro\ApiProblem\Http;
+
+use Phpro\ApiProblem\Http\HttpApiProblem;
+use Phpro\ApiProblem\Http\IAmATeapotProblem;
+use PhpSpec\ObjectBehavior;
+
+class IAmATeapotProblemSpec extends ObjectBehavior
+{
+    public function let(): void
+    {
+        $this->beConstructedWith('i am a teapot');
+    }
+
+    public function it_is_initializable(): void
+    {
+        $this->shouldHaveType(IAmATeapotProblem::class);
+    }
+
+    public function it_is_an_http_api_problem(): void
+    {
+        $this->shouldHaveType(HttpApiProblem::class);
+    }
+
+    public function it_can_parse_to_array(): void
+    {
+        $this->toArray()->shouldBe([
+            'status' => 418,
+            'type' => HttpApiProblem::TYPE_HTTP_RFC,
+            'title' => HttpApiProblem::getTitleForStatusCode(418),
+            'detail' => 'i am a teapot',
+        ]);
+    }
+}
diff --git a/spec/Http/LockedProblemSpec.php b/spec/Http/LockedProblemSpec.php
new file mode 100644
index 0000000..c44dfa8
--- /dev/null
+++ b/spec/Http/LockedProblemSpec.php
@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace spec\Phpro\ApiProblem\Http;
+
+use Phpro\ApiProblem\Http\HttpApiProblem;
+use Phpro\ApiProblem\Http\LockedProblem;
+use PhpSpec\ObjectBehavior;
+
+class LockedProblemSpec extends ObjectBehavior
+{
+    public function let(): void
+    {
+        $this->beConstructedWith('locked');
+    }
+
+    public function it_is_initializable(): void
+    {
+        $this->shouldHaveType(LockedProblem::class);
+    }
+
+    public function it_is_an_http_api_problem(): void
+    {
+        $this->shouldHaveType(HttpApiProblem::class);
+    }
+
+    public function it_can_parse_to_array(): void
+    {
+        $this->toArray()->shouldBe([
+            'status' => 423,
+            'type' => HttpApiProblem::TYPE_HTTP_RFC,
+            'title' => HttpApiProblem::getTitleForStatusCode(423),
+            'detail' => 'locked',
+        ]);
+    }
+}
diff --git a/spec/Http/MethodNotAllowedProblemSpec.php b/spec/Http/MethodNotAllowedProblemSpec.php
new file mode 100644
index 0000000..23f00f3
--- /dev/null
+++ b/spec/Http/MethodNotAllowedProblemSpec.php
@@ -0,0 +1,65 @@
+<?php
+
+declare(strict_types=1);
+
+namespace spec\Phpro\ApiProblem\Http;
+
+use Phpro\ApiProblem\Http\HttpApiProblem;
+use Phpro\ApiProblem\Http\MethodNotAllowedProblem;
+use PhpSpec\ObjectBehavior;
+
+class MethodNotAllowedProblemSpec extends ObjectBehavior
+{
+    public function let(): void
+    {
+        $this->beConstructedWith('method not allowed');
+    }
+
+    public function it_is_initializable(): void
+    {
+        $this->shouldHaveType(MethodNotAllowedProblem::class);
+    }
+
+    public function it_is_an_http_api_problem(): void
+    {
+        $this->shouldHaveType(HttpApiProblem::class);
+    }
+
+    public function it_can_parse_to_array(): void
+    {
+        $this->toArray()->shouldBe([
+            'status' => 405,
+            'type' => HttpApiProblem::TYPE_HTTP_RFC,
+            'title' => HttpApiProblem::getTitleForStatusCode(405),
+            'detail' => 'method not allowed',
+        ]);
+    }
+
+    public function it_should_be_an_allowed_method_with_multiple_methods(): void
+    {
+        $allowedMethods = ['POST', 'GET'];
+        $currentMethod = 'OPTIONS';
+
+        $this->beConstructedThrough('invalidMethod', [$allowedMethods, $currentMethod]);
+        $this->toArray()->shouldBe([
+            'status' => 405,
+            'type' => HttpApiProblem::TYPE_HTTP_RFC,
+            'title' => HttpApiProblem::getTitleForStatusCode(405),
+            'detail' => 'OPTIONS not allowed. Should be: POST or GET',
+        ]);
+    }
+
+    public function it_should_be_an_allowed_method_with_a_single_methods(): void
+    {
+        $allowedMethods = ['POST'];
+        $currentMethod = 'OPTIONS';
+
+        $this->beConstructedThrough('invalidMethod', [$allowedMethods, $currentMethod]);
+        $this->toArray()->shouldBe([
+            'status' => 405,
+            'type' => HttpApiProblem::TYPE_HTTP_RFC,
+            'title' => HttpApiProblem::getTitleForStatusCode(405),
+            'detail' => 'OPTIONS not allowed. Should be: POST',
+        ]);
+    }
+}
diff --git a/spec/Http/PreconditionFailedProblemSpec.php b/spec/Http/PreconditionFailedProblemSpec.php
new file mode 100644
index 0000000..db0d10f
--- /dev/null
+++ b/spec/Http/PreconditionFailedProblemSpec.php
@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace spec\Phpro\ApiProblem\Http;
+
+use Phpro\ApiProblem\Http\HttpApiProblem;
+use Phpro\ApiProblem\Http\PreconditionFailedProblem;
+use PhpSpec\ObjectBehavior;
+
+class PreconditionFailedProblemSpec extends ObjectBehavior
+{
+    public function let(): void
+    {
+        $this->beConstructedWith('precondition failed');
+    }
+
+    public function it_is_initializable(): void
+    {
+        $this->shouldHaveType(PreconditionFailedProblem::class);
+    }
+
+    public function it_is_an_http_api_problem(): void
+    {
+        $this->shouldHaveType(HttpApiProblem::class);
+    }
+
+    public function it_can_parse_to_array(): void
+    {
+        $this->toArray()->shouldBe([
+            'status' => 412,
+            'type' => HttpApiProblem::TYPE_HTTP_RFC,
+            'title' => HttpApiProblem::getTitleForStatusCode(412),
+            'detail' => 'precondition failed',
+        ]);
+    }
+}
diff --git a/spec/Http/PreconditionRequiredProblemSpec.php b/spec/Http/PreconditionRequiredProblemSpec.php
new file mode 100644
index 0000000..a124aee
--- /dev/null
+++ b/spec/Http/PreconditionRequiredProblemSpec.php
@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace spec\Phpro\ApiProblem\Http;
+
+use Phpro\ApiProblem\Http\HttpApiProblem;
+use Phpro\ApiProblem\Http\PreconditionRequiredProblem;
+use PhpSpec\ObjectBehavior;
+
+class PreconditionRequiredProblemSpec extends ObjectBehavior
+{
+    public function let(): void
+    {
+        $this->beConstructedWith('precondition required');
+    }
+
+    public function it_is_initializable(): void
+    {
+        $this->shouldHaveType(PreconditionRequiredProblem::class);
+    }
+
+    public function it_is_an_http_api_problem(): void
+    {
+        $this->shouldHaveType(HttpApiProblem::class);
+    }
+
+    public function it_can_parse_to_array(): void
+    {
+        $this->toArray()->shouldBe([
+            'status' => 428,
+            'type' => HttpApiProblem::TYPE_HTTP_RFC,
+            'title' => HttpApiProblem::getTitleForStatusCode(428),
+            'detail' => 'precondition required',
+        ]);
+    }
+}
diff --git a/spec/Http/UnprocessableEntityProblemSpec.php b/spec/Http/UnprocessableEntityProblemSpec.php
new file mode 100644
index 0000000..c172575
--- /dev/null
+++ b/spec/Http/UnprocessableEntityProblemSpec.php
@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace spec\Phpro\ApiProblem\Http;
+
+use Phpro\ApiProblem\Http\HttpApiProblem;
+use Phpro\ApiProblem\Http\UnprocessableEntityProblem;
+use PhpSpec\ObjectBehavior;
+
+class UnprocessableEntityProblemSpec extends ObjectBehavior
+{
+    public function let(): void
+    {
+        $this->beConstructedWith('unprocessable entity');
+    }
+
+    public function it_is_initializable(): void
+    {
+        $this->shouldHaveType(UnprocessableEntityProblem::class);
+    }
+
+    public function it_is_an_http_api_problem(): void
+    {
+        $this->shouldHaveType(HttpApiProblem::class);
+    }
+
+    public function it_can_parse_to_array(): void
+    {
+        $this->toArray()->shouldBe([
+            'status' => 422,
+            'type' => HttpApiProblem::TYPE_HTTP_RFC,
+            'title' => HttpApiProblem::getTitleForStatusCode(422),
+            'detail' => 'unprocessable entity',
+        ]);
+    }
+}
diff --git a/spec/Http/UnsupportedMediaTypeProblemSpec.php b/spec/Http/UnsupportedMediaTypeProblemSpec.php
new file mode 100644
index 0000000..5873743
--- /dev/null
+++ b/spec/Http/UnsupportedMediaTypeProblemSpec.php
@@ -0,0 +1,65 @@
+<?php
+
+declare(strict_types=1);
+
+namespace spec\Phpro\ApiProblem\Http;
+
+use Phpro\ApiProblem\Http\HttpApiProblem;
+use Phpro\ApiProblem\Http\UnsupportedMediaTypeProblem;
+use PhpSpec\ObjectBehavior;
+
+class UnsupportedMediaTypeProblemSpec extends ObjectBehavior
+{
+    public function let(): void
+    {
+        $this->beConstructedWith('unsupported media type');
+    }
+
+    public function it_is_initializable(): void
+    {
+        $this->shouldHaveType(UnsupportedMediaTypeProblem::class);
+    }
+
+    public function it_is_an_http_api_problem(): void
+    {
+        $this->shouldHaveType(HttpApiProblem::class);
+    }
+
+    public function it_can_parse_to_array(): void
+    {
+        $this->toArray()->shouldBe([
+            'status' => 415,
+            'type' => HttpApiProblem::TYPE_HTTP_RFC,
+            'title' => HttpApiProblem::getTitleForStatusCode(415),
+            'detail' => 'unsupported media type',
+        ]);
+    }
+
+    public function it_should_be_a_media_type_with_allowed_content_encodings(): void
+    {
+        $allowedEncodings = ['gzip', 'identity'];
+        $currentEncoding = ['compress', 'none'];
+
+        $this->beConstructedThrough('invalidContentEncoding', [$allowedEncodings, $currentEncoding]);
+        $this->toArray()->shouldBe([
+            'status' => 415,
+            'type' => HttpApiProblem::TYPE_HTTP_RFC,
+            'title' => HttpApiProblem::getTitleForStatusCode(415),
+            'detail' => 'compress and none not allowed. Should be: gzip or identity',
+        ]);
+    }
+
+    public function it_should_be_a_media_type_with_allowed_content_types(): void
+    {
+        $allowedEncodings = ['text/html', 'multipart/form-data'];
+        $currentEncoding = 'application/json';
+
+        $this->beConstructedThrough('invalidContentType', [$allowedEncodings, $currentEncoding]);
+        $this->toArray()->shouldBe([
+            'status' => 415,
+            'type' => HttpApiProblem::TYPE_HTTP_RFC,
+            'title' => HttpApiProblem::getTitleForStatusCode(415),
+            'detail' => 'application/json not allowed. Should be: text/html or multipart/form-data',
+        ]);
+    }
+}
diff --git a/src/Http/IAmATeapotProblem.php b/src/Http/IAmATeapotProblem.php
new file mode 100644
index 0000000..4034388
--- /dev/null
+++ b/src/Http/IAmATeapotProblem.php
@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phpro\ApiProblem\Http;
+
+class IAmATeapotProblem extends HttpApiProblem
+{
+    public function __construct(string $detail)
+    {
+        parent::__construct(418, [
+            'detail' => $detail,
+        ]);
+    }
+}
diff --git a/src/Http/LockedProblem.php b/src/Http/LockedProblem.php
new file mode 100644
index 0000000..e2610a7
--- /dev/null
+++ b/src/Http/LockedProblem.php
@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phpro\ApiProblem\Http;
+
+class LockedProblem extends HttpApiProblem
+{
+    public function __construct(string $detail)
+    {
+        parent::__construct(423, [
+            'detail' => $detail,
+        ]);
+    }
+}
diff --git a/src/Http/MethodNotAllowedProblem.php b/src/Http/MethodNotAllowedProblem.php
new file mode 100644
index 0000000..ab315e4
--- /dev/null
+++ b/src/Http/MethodNotAllowedProblem.php
@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phpro\ApiProblem\Http;
+
+class MethodNotAllowedProblem extends HttpApiProblem
+{
+    public function __construct(string $detail)
+    {
+        parent::__construct(405, [
+            'detail' => $detail,
+        ]);
+    }
+
+    public static function invalidMethod(array $allowMethods, string $currentMethod): self
+    {
+        $allowMethods[] = implode(' or ', array_splice($allowMethods, -2));
+        $detail = $currentMethod.' not allowed. Should be: '.implode(', ', $allowMethods);
+
+        return new self($detail);
+    }
+}
diff --git a/src/Http/PreconditionFailedProblem.php b/src/Http/PreconditionFailedProblem.php
new file mode 100644
index 0000000..1815ac7
--- /dev/null
+++ b/src/Http/PreconditionFailedProblem.php
@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phpro\ApiProblem\Http;
+
+class PreconditionFailedProblem extends HttpApiProblem
+{
+    public function __construct(string $detail)
+    {
+        parent::__construct(412, [
+            'detail' => $detail,
+        ]);
+    }
+}
diff --git a/src/Http/PreconditionRequiredProblem.php b/src/Http/PreconditionRequiredProblem.php
new file mode 100644
index 0000000..fabc946
--- /dev/null
+++ b/src/Http/PreconditionRequiredProblem.php
@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phpro\ApiProblem\Http;
+
+class PreconditionRequiredProblem extends HttpApiProblem
+{
+    public function __construct(string $detail)
+    {
+        parent::__construct(428, [
+            'detail' => $detail,
+        ]);
+    }
+}
diff --git a/src/Http/UnprocessableEntityProblem.php b/src/Http/UnprocessableEntityProblem.php
new file mode 100644
index 0000000..9ff4429
--- /dev/null
+++ b/src/Http/UnprocessableEntityProblem.php
@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phpro\ApiProblem\Http;
+
+class UnprocessableEntityProblem extends HttpApiProblem
+{
+    public function __construct(string $detail)
+    {
+        parent::__construct(422, [
+            'detail' => $detail,
+        ]);
+    }
+}
diff --git a/src/Http/UnsupportedMediaTypeProblem.php b/src/Http/UnsupportedMediaTypeProblem.php
new file mode 100644
index 0000000..468cbd1
--- /dev/null
+++ b/src/Http/UnsupportedMediaTypeProblem.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phpro\ApiProblem\Http;
+
+class UnsupportedMediaTypeProblem extends HttpApiProblem
+{
+    public function __construct(string $detail)
+    {
+        parent::__construct(415, [
+            'detail' => $detail,
+        ]);
+    }
+
+    public static function invalidContentEncoding(array $allowedEncodings, array $providedEncodings): self
+    {
+        $allowedEncodings[] = implode(' or ', array_splice($allowedEncodings, -2));
+        $providedEncodings[] = implode(' and ', array_splice($providedEncodings, -2));
+
+        $detail = implode(', ', $providedEncodings).' not allowed. Should be: '.implode(', ', $allowedEncodings);
+
+        return new self($detail);
+    }
+
+    public static function invalidContentType(array $allowedTypes, string $providedType): self
+    {
+        $allowedTypes[] = implode(' or ', array_splice($allowedTypes, -2));
+
+        $detail = $providedType.' not allowed. Should be: '.implode(', ', $allowedTypes);
+
+        return new self($detail);
+    }
+}