diff --git a/src/Normalizer/DeterministicNormalizerInterface.php b/src/Normalizer/DeterministicNormalizerInterface.php
index f40ca7e..a1a816c 100644
--- a/src/Normalizer/DeterministicNormalizerInterface.php
+++ b/src/Normalizer/DeterministicNormalizerInterface.php
@@ -11,4 +11,20 @@ use Symfony\Component\Serializer\Normalizer\NormalizerInterface;
  * for *any* instance of a particular interface or class if it is also valid for
  * the given format, regardless of the state of the $data or $context arguments.
  */
-interface DeterministicNormalizerInterface extends NormalizerInterface {}
+interface DeterministicNormalizerInterface extends NormalizerInterface {
+
+  /**
+   * The interface or class that this Normalizer supports.
+   *
+   * @param string|object $type
+   *   An interface or class name or an object.
+   * @param string $format
+   *   Format the normalization result will be encoded as.
+   *
+   * @return bool
+   *   Whether this normalizer supports *any* instance of the given interface or
+   *   class or of the given object's class.
+   */
+  public function supportsNormalizationForInterfaceOrClass($type, $format);
+
+}
diff --git a/src/Normalizer/NormalizerBase.php b/src/Normalizer/NormalizerBase.php
index b5a642c..7caae87 100644
--- a/src/Normalizer/NormalizerBase.php
+++ b/src/Normalizer/NormalizerBase.php
@@ -16,6 +16,16 @@ abstract class NormalizerBase extends SerializationNormalizerBase implements Det
    */
   protected $format = 'api_json';
 
+  /**
+   * {@inheritdoc}
+   */
+  public function supportsNormalizationForInterfaceOrClass($type, $format) {
+    $supported = (array) $this->supportedInterfaceOrClass;
+    return $this->checkFormat($format) && (bool) array_filter($supported, function ($name) use ($type) {
+      return is_subclass_of($type, $name);
+    });
+  }
+
   /**
    * {@inheritdoc}
    */
diff --git a/src/Serializer/Serializer.php b/src/Serializer/Serializer.php
index 5437522..59a0688 100644
--- a/src/Serializer/Serializer.php
+++ b/src/Serializer/Serializer.php
@@ -96,6 +96,7 @@ final class Serializer extends SymfonySerializer {
     }
     $normalizer = $this->copiedGetNormalizer($data, $format, $context);
     if ($type && $normalizer instanceof DeterministicNormalizerInterface) {
+      assert($normalizer->supportsNormalizationForInterfaceOrClass($type, $format));
       $this->deterministicNormalizers[$type][$format] = $normalizer;
     }
     return $normalizer;