core/modules/rest/src/RequestHandler.php | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/core/modules/rest/src/RequestHandler.php b/core/modules/rest/src/RequestHandler.php
index 8442682..ca8318e 100644
--- a/core/modules/rest/src/RequestHandler.php
+++ b/core/modules/rest/src/RequestHandler.php
@@ -162,8 +162,12 @@ protected function getArgumentResolver(RouteMatchInterface $route_match, $unseri
     $route_arguments = $route_match->getParameters()->all();
     $upcasted_route_arguments = $route_arguments;
 
-    // Just set the values, if they are actually defined, otherwise, the
-    // argument resolver believe
+    // \Drupal\rest\Plugin\ResourceInterface plugins historically receive the
+    // unserialized request body as the N+1th method argument, where N is the
+    // number of route parameters specified on the accompanying route. To be
+    // able to use the argument resolver, which is not based on position but on
+    // name and typehint, specify commonly used names here. 0 or 1 of these will
+    // be used.
     if (isset($unserialized)) {
       $upcasted_route_arguments['entity'] = $unserialized;
       $upcasted_route_arguments['data'] = $unserialized;
@@ -172,8 +176,8 @@ protected function getArgumentResolver(RouteMatchInterface $route_match, $unseri
 
     // In the case of GET the entity is stored in $upcasted_route_arguments in
     // the $entity_type_id key, not as 'entity', which
-    // \Drupal\rest\Plugin\rest\resource\EntityResource expects as their name.
-    if (empty($upcasted_route_arguments['entity'])) {
+    // \Drupal\rest\Plugin\rest\resource\EntityResource::get() expects as their name.
+    if (!in_array($request->getMethod(), ['PATCH', 'POST'], TRUE) && empty($upcasted_route_arguments['entity'])) {
       // Try to find a parameter which is an entity.
       foreach ($route_arguments as $value) {
         if ($value instanceof EntityInterface) {
@@ -182,7 +186,7 @@ protected function getArgumentResolver(RouteMatchInterface $route_match, $unseri
       }
     }
 
-    if (empty($upcasted_route_arguments['original_entity'])) {
+    if (in_array($request->getMethod(), ['PATCH', 'POST'], TRUE) && empty($upcasted_route_arguments['original_entity'])) {
       // Try to find a parameter which is an entity.
       foreach ($route_arguments as $value) {
         if ($value instanceof EntityInterface) {
@@ -198,7 +202,9 @@ protected function getArgumentResolver(RouteMatchInterface $route_match, $unseri
     if (isset($request)) {
       $wildcard_arguments[] = $request;
     }
-    $wildcard_arguments[] = $unserialized;
+    if (isset($unserialized)) {
+      $wildcard_arguments[] = $unserialized;
+    }
 
     return new ArgumentsResolver($raw_route_arguments, $upcasted_route_arguments, $wildcard_arguments);
   }