diff --git a/src/UnresolvedValueException.php b/src/UnresolvedValueException.php
index c4c992e..0e1d38b 100644
--- a/src/UnresolvedValueException.php
+++ b/src/UnresolvedValueException.php
@@ -29,7 +29,7 @@ public static function unresolvedParameter(\ReflectionParameter $parameter) : Un
      */
     public static function unresolvedProperty(\ReflectionProperty $property) : UnresolvedValueException
     {
-        $message = 'The property %s::$%s could not be resolved';
+        $message = 'The property %s::$%s could not be resolved.';
         $message = sprintf($message, $property->getDeclaringClass()->getName(), $property->getName());
 
         return new self($message);
@@ -47,12 +47,27 @@ private static function getParameterName(\ReflectionParameter $parameter) : stri
         $parameterType = '';
 
         if (null !== $type = $parameter->getType()) {
-            $parameterType = (string) $type . ' ';
+            $parameterType = self::getReflectionTypeName($type) . ' ';
         }
 
         return $parameterType . '$' . $parameter->getName();
     }
 
+    private static function getReflectionTypeName(\ReflectionType $reflectionType)
+    {
+        if ($reflectionType instanceof \ReflectionNamedType) {
+            return $reflectionType->getName();
+        }
+
+        if ($reflectionType instanceof \ReflectionUnionType) {
+            return implode('|', array_map(function(\ReflectionNamedType $type) {
+                return $type->getName();
+            }, $reflectionType->getTypes()));
+        }
+
+        return '';
+    }
+
     /**
      * Returns the type (if any) + name of a function.
      *