diff --git a/core/modules/rest/src/Entity/RestEndpoint.php b/core/modules/rest/src/Entity/RestEndpoint.php
index 7769a55..1d56c06 100644
--- a/core/modules/rest/src/Entity/RestEndpoint.php
+++ b/core/modules/rest/src/Entity/RestEndpoint.php
@@ -88,6 +88,7 @@ public function getResourcePlugin() {
    * {@inheritdoc}
    */
   public function getSupportedAuthenticationProviders($method) {
+    $method = $this->normaliseRestMethod($method);
     if (isset($this->configuration[$method]) && isset($this->configuration[$method]['supported_auth'])) {
       return $this->configuration[$method]['supported_auth'];
     }
@@ -98,11 +99,13 @@ public function getSupportedAuthenticationProviders($method) {
    * {@inheritdoc}
    */
   public function hasSupportForAuthenticationProvider($method, $auth) {
+    $method = $this->normaliseRestMethod($method);
     return $this->hasSupportedAuthenticationProviders($method)
            && in_array($auth, $this->configuration[$method]['supported_auth']);
   }
 
   public function hasSupportedAuthenticationProviders($method) {
+    $method = $this->normaliseRestMethod($method);
     return isset($this->configuration[$method])
            && isset($this->configuration[$method]['supported_auth'])
            && !empty($this->configuration[$method]['supported_auth']);
@@ -112,6 +115,7 @@ public function hasSupportedAuthenticationProviders($method) {
    * {@inheritdoc}
    */
   public function addSupportedAuthenticationProvider($method, $auth) {
+    $method = $this->normaliseRestMethod($method);
     if (!isset($this->configuration[$method])) {
       $this->configuration[$method] = [ 'supported_auth' => [] ];
     }
@@ -128,6 +132,7 @@ public function addSupportedAuthenticationProvider($method, $auth) {
    * {@inheritdoc}
    */
   public function removeSupportedAuthenticationProvider($method, $auth) {
+    $method = $this->normaliseRestMethod($method);
     $new_auth = array_filter($this->configuration[$method]['supported_auth'], function ($val) use ($auth) {
       return ($val != $auth);
     });
@@ -139,6 +144,7 @@ public function removeSupportedAuthenticationProvider($method, $auth) {
    * {@inheritdoc}
    */
   public function getSupportedFormats($method) {
+    $method = $this->normaliseRestMethod($method);
     if (isset($this->configuration[$method]) && isset($this->configuration[$method]['supported_formats'])) {
       return $this->configuration[$method]['supported_formats'];
     }
@@ -149,6 +155,7 @@ public function getSupportedFormats($method) {
    * {@inheritdoc}
    */
   public function supportsFormat($method, $format) {
+    $method = $this->normaliseRestMethod($method);
     return $this->hasSupportedFormats($method)
            && in_array($format, $this->configuration[$method]['supported_formats']);
   }
@@ -157,6 +164,7 @@ public function supportsFormat($method, $format) {
    * {@inheritdoc}
    */
   public function hasSupportedFormats($method) {
+    $method = $this->normaliseRestMethod($method);
     return isset($this->configuration[$method])
            && isset($this->configuration[$method]['supported_formats'])
            && !empty($this->configuration[$method]['supported_formats']);
@@ -166,6 +174,7 @@ public function hasSupportedFormats($method) {
    * {@inheritdoc}
    */
   public function addSupportedFormat($method, $format) {
+    $method = $this->normaliseRestMethod($method);
     if (!isset($this->configuration[$method])) {
       $this->configuration[$method] = [ 'supported_formats' => [] ];
     }
@@ -182,6 +191,7 @@ public function addSupportedFormat($method, $format) {
    * {@inheritdoc}
    */
   public function removeSupportedFormat($method, $format) {
+    $method = $this->normaliseRestMethod($method);
     $new_auth = array_filter($this->configuration[$method]['supported_formats'], function ($val) use ($format) {
       return ($val != $format);
     });
@@ -202,4 +212,13 @@ public function getPluginCollections() {
       'resource' => new DefaultLazyPluginCollection($this->pluginManager, $plugin_configuration)
     ];
   }
+
+  protected function normaliseRestMethod($method) {
+    $valid_methods = [ 'GET', 'POST', 'PATCH', 'DELETE' ];
+    $normalised_method = strtoupper($method);
+    if (!in_array($normalised_method, $valid_methods)) {
+      throw new \InvalidArgumentException('The method is not supported.');
+    }
+    return $normalised_method;
+  }
 }