diff --git a/Encoder/XmlEncoder.php b/Encoder/XmlEncoder.php
index 138f9280d..fbfa75746 100644
--- a/Encoder/XmlEncoder.php
+++ b/Encoder/XmlEncoder.php
@@ -473,7 +473,7 @@ private function buildXml(\DOMNode $parentNode, $data, string $xmlRootNodeName =
             return $this->appendNode($parentNode, $data, 'data');
         }
 
-        throw new NotEncodableValueException(sprintf('An unexpected value could not be serialized: %s.', !\is_resource($data) ? var_export($data, true) : sprintf('%s resource', get_resource_type($data))));
+        throw new NotEncodableValueException('An unexpected value could not be serialized: '.(!\is_resource($data) ? var_export($data, true) : sprintf('%s resource', get_resource_type($data))));
     }
 
     /**
diff --git a/Serializer.php b/Serializer.php
index 947704847..3f2461cf9 100644
--- a/Serializer.php
+++ b/Serializer.php
@@ -173,7 +173,7 @@ public function normalize($data, $format = null, array $context = [])
             throw new NotNormalizableValueException(sprintf('Could not normalize object of type "%s", no supporting normalizer found.', \get_class($data)));
         }
 
-        throw new NotNormalizableValueException(sprintf('An unexpected value could not be normalized: %s.', !\is_resource($data) ? var_export($data, true) : sprintf('%s resource', get_resource_type($data))));
+        throw new NotNormalizableValueException('An unexpected value could not be normalized: '.(!\is_resource($data) ? var_export($data, true) : sprintf('%s resource', get_resource_type($data))));
     }
 
     /**