diff -u b/src/Context/FieldResolver.php b/src/Context/FieldResolver.php
--- b/src/Context/FieldResolver.php
+++ b/src/Context/FieldResolver.php
@@ -124,6 +124,11 @@
       throw new BadRequestHttpException('No field name was provided for the filter.');
     }
 
+    $entity_type = \Drupal::entityTypeManager()->getDefinition($entity_type_id);
+    if (!$entity_type->entityClassImplements(FieldableEntityInterface::class)){
+      return $resource_type->getInternalName($external_field_name);
+    }
+
     // Turns 'uid.categories.name' into
     // 'uid.entity.field_category.entity.name'. This may be too simple, but it
     // works for the time being.
@@ -134,10 +139,6 @@
     while ($part = array_shift($parts)) {
       $field_name = $this->getInternalName($part, $resource_types);
 
-      $entity_type = \Drupal::entityTypeManager()->getDefinition($entity_type_id);
-      if (!$entity_type->entityClassImplements(FieldableEntityInterface::class)){
-        return $field_name;
-      }
       $candidate_definitions = $this->getFieldItemDefinitions(
         $resource_types,
         $field_name