diff --git a/src/Api/Exception/InvalidAccessTokenException.php b/src/Api/Exception/InvalidAccessTokenException.php
index ec8824636..94ac90952 100644
--- a/src/Api/Exception/InvalidAccessTokenException.php
+++ b/src/Api/Exception/InvalidAccessTokenException.php
@@ -10,7 +10,12 @@
 namespace Flarum\Api\Exception;
 
 use Exception;
+use Flarum\Foundation\KnownError;
 
-class InvalidAccessTokenException extends Exception
+class InvalidAccessTokenException extends Exception implements KnownError
 {
+    public function getType(): string
+    {
+        return 'invalid_access_token';
+    }
 }
diff --git a/src/Http/Exception/ForbiddenException.php b/src/Http/Exception/ForbiddenException.php
index e178249f6..88c6555f0 100644
--- a/src/Http/Exception/ForbiddenException.php
+++ b/src/Http/Exception/ForbiddenException.php
@@ -10,11 +10,12 @@
 namespace Flarum\Http\Exception;
 
 use Exception;
+use Flarum\Foundation\KnownError;
 
-class ForbiddenException extends Exception
+class ForbiddenException extends Exception implements KnownError
 {
-    public function __construct($message = null, $code = 403, Exception $previous = null)
+    public function getType(): string
     {
-        parent::__construct($message, $code, $previous);
+        return 'forbidden';
     }
 }
diff --git a/src/Http/Exception/MethodNotAllowedException.php b/src/Http/Exception/MethodNotAllowedException.php
index d22fa3865..a416c0d0f 100644
--- a/src/Http/Exception/MethodNotAllowedException.php
+++ b/src/Http/Exception/MethodNotAllowedException.php
@@ -10,11 +10,12 @@
 namespace Flarum\Http\Exception;
 
 use Exception;
+use Flarum\Foundation\KnownError;
 
-class MethodNotAllowedException extends Exception
+class MethodNotAllowedException extends Exception implements KnownError
 {
-    public function __construct($message = null, $code = 405, Exception $previous = null)
+    public function getType(): string
     {
-        parent::__construct($message, $code, $previous);
+        return 'method_not_allowed';
     }
 }
diff --git a/src/Http/Exception/RouteNotFoundException.php b/src/Http/Exception/RouteNotFoundException.php
index 771c2cc24..ca41fc92a 100644
--- a/src/Http/Exception/RouteNotFoundException.php
+++ b/src/Http/Exception/RouteNotFoundException.php
@@ -10,11 +10,12 @@
 namespace Flarum\Http\Exception;
 
 use Exception;
+use Flarum\Foundation\KnownError;
 
-class RouteNotFoundException extends Exception
+class RouteNotFoundException extends Exception implements KnownError
 {
-    public function __construct($message = null, $code = 404, Exception $previous = null)
+    public function getType(): string
     {
-        parent::__construct($message, $code, $previous);
+        return 'route_not_found';
     }
 }
diff --git a/src/Http/Exception/TokenMismatchException.php b/src/Http/Exception/TokenMismatchException.php
index fc3225f47..a0c20c0f8 100644
--- a/src/Http/Exception/TokenMismatchException.php
+++ b/src/Http/Exception/TokenMismatchException.php
@@ -10,11 +10,12 @@
 namespace Flarum\Http\Exception;
 
 use Exception;
+use Flarum\Foundation\KnownError;
 
-class TokenMismatchException extends Exception
+class TokenMismatchException extends Exception implements KnownError
 {
-    public function __construct($message = null, $code = 419, Exception $previous = null)
+    public function getType(): string
     {
-        parent::__construct($message, $code, $previous);
+        return 'csrf_token_mismatch';
     }
 }
diff --git a/src/Post/Exception/FloodingException.php b/src/Post/Exception/FloodingException.php
index 6cf786026..8c5b39d89 100644
--- a/src/Post/Exception/FloodingException.php
+++ b/src/Post/Exception/FloodingException.php
@@ -10,7 +10,12 @@
 namespace Flarum\Post\Exception;
 
 use Exception;
+use Flarum\Foundation\KnownError;
 
-class FloodingException extends Exception
+class FloodingException extends Exception implements KnownError
 {
+    public function getType(): string
+    {
+        return 'too_many_requests';
+    }
 }
diff --git a/src/User/Exception/InvalidConfirmationTokenException.php b/src/User/Exception/InvalidConfirmationTokenException.php
index 0eb89b57e..e06e7ef2e 100644
--- a/src/User/Exception/InvalidConfirmationTokenException.php
+++ b/src/User/Exception/InvalidConfirmationTokenException.php
@@ -10,7 +10,12 @@
 namespace Flarum\User\Exception;
 
 use Exception;
+use Flarum\Foundation\KnownError;
 
-class InvalidConfirmationTokenException extends Exception
+class InvalidConfirmationTokenException extends Exception implements KnownError
 {
+    public function getType(): string
+    {
+        return 'invalid_confirmation_token';
+    }
 }
diff --git a/src/User/Exception/PermissionDeniedException.php b/src/User/Exception/PermissionDeniedException.php
index 22097af8f..cebe8db80 100644
--- a/src/User/Exception/PermissionDeniedException.php
+++ b/src/User/Exception/PermissionDeniedException.php
@@ -10,11 +10,12 @@
 namespace Flarum\User\Exception;
 
 use Exception;
+use Flarum\Foundation\KnownError;
 
-class PermissionDeniedException extends Exception
+class PermissionDeniedException extends Exception implements KnownError
 {
-    public function __construct($message = null, $code = 403, Exception $previous = null)
+    public function getType(): string
     {
-        parent::__construct($message, $code, $previous);
+        return 'permission_denied';
     }
 }