diff --git a/core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/PrimitiveTypeConstraintValidator.php b/core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/PrimitiveTypeConstraintValidator.php
index daaaa45..8444f95 100644
--- a/core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/PrimitiveTypeConstraintValidator.php
+++ b/core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/PrimitiveTypeConstraintValidator.php
@@ -52,7 +52,7 @@ public function validate($value, Constraint $constraint) {
     // Unfortunately, this cannot use filter_var() with FILTER_VALIDATE_URL,
     // because it doesn't correctly validate URLs.
     // @see http://php.net/manual/de/filter.filters.validate.php#110411
-    if ($typed_data instanceof UriInterface && parse_url($value, PHP_URL_SCHEME) === FALSE) {
+    if ($typed_data instanceof UriInterface && parse_url($value, PHP_URL_SCHEME) === NULL) {
       $valid = FALSE;
     }
     // @todo: Move those to separate constraint validators.
diff --git a/core/modules/link/src/Plugin/Validation/Constraint/LinkTypeConstraint.php b/core/modules/link/src/Plugin/Validation/Constraint/LinkTypeConstraint.php
index def43ac..7661838 100644
--- a/core/modules/link/src/Plugin/Validation/Constraint/LinkTypeConstraint.php
+++ b/core/modules/link/src/Plugin/Validation/Constraint/LinkTypeConstraint.php
@@ -7,8 +7,6 @@
 
 namespace Drupal\link\Plugin\Validation\Constraint;
 
-use Drupal\Component\Utility\UrlHelper;
-use Drupal\Core\Url;
 use Drupal\link\LinkItemInterface;
 use Symfony\Component\Validator\Constraint;
 use Symfony\Component\Validator\ConstraintValidatorInterface;
diff --git a/core/tests/Drupal/Tests/Core/Validation/Plugin/Validation/Constraint/PrimitiveTypeConstraintValidatorTest.php b/core/tests/Drupal/Tests/Core/Validation/Plugin/Validation/Constraint/PrimitiveTypeConstraintValidatorTest.php
new file mode 100644
index 0000000..8319d5b
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Validation/Plugin/Validation/Constraint/PrimitiveTypeConstraintValidatorTest.php
@@ -0,0 +1,83 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\Core\Validation\Plugin\Validation\Constraint\PrimitiveTypeConstraintValidatorTest.
+ */
+
+namespace Drupal\Tests\Core\Validation\Plugin\Validation\Constraint;
+
+use Drupal\Core\TypedData\PrimitiveInterface;
+use Drupal\Core\Validation\Plugin\Validation\Constraint\PrimitiveTypeConstraint;
+use Drupal\Core\Validation\Plugin\Validation\Constraint\PrimitiveTypeConstraintValidator;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @coversDefaultClass Drupal\Core\Validation\Plugin\Validation\Constraint\PrimitiveTypeConstraintValidator
+ * @group validation
+ */
+class PrimitiveTypeConstraintValidatorTest extends UnitTestCase {
+
+  /**
+   * @covers ::validate
+   *
+   * @dataProvider provideTestValidate
+   */
+  public function testValidate(PrimitiveInterface $typed_data, $value, $valid) {
+    $metadata = $this->getMockBuilder('Drupal\Core\TypedData\Validation\Metadata')
+      ->disableOriginalConstructor()
+      ->getMock();
+    $metadata->expects($this->any())
+      ->method('getTypedData')
+      ->willReturn($typed_data);
+
+    $context = $this->getMock('Symfony\Component\Validator\ExecutionContextInterface');
+    $context->expects($this->any())
+      ->method('getMetadata')
+      ->willReturn($metadata);
+
+    if ($valid) {
+      $context->expects($this->never())
+        ->method('addViolation');
+    }
+    else {
+      $context->expects($this->once())
+        ->method('addViolation');
+    }
+
+    $constraint = new PrimitiveTypeConstraint();
+
+    $validate = new PrimitiveTypeConstraintValidator();
+    $validate->initialize($context);
+    $validate->validate($value, $constraint);
+  }
+
+  public function provideTestValidate() {
+    $data = [];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\BooleanInterface'), NULL, TRUE];
+
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\BooleanInterface'), 1, TRUE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\BooleanInterface'), 'test', FALSE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\FloatInterface'), 1.5, TRUE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\FloatInterface'), 'test', FALSE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\IntegerInterface'), 1, TRUE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\IntegerInterface'), 1.5, FALSE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\IntegerInterface'), 'test', FALSE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\StringInterface'), 'test', TRUE];
+    // It is odd that 1 is a valid string.
+    // $data[] = [$this->getMock('Drupal\Core\TypedData\Type\StringInterface'), 1, FALSE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\StringInterface'), [], FALSE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\UriInterface'), 'http://www.drupal.org', TRUE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\UriInterface'), 'https://www.drupal.org', TRUE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\UriInterface'), 'Invalid', FALSE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\UriInterface'), 'entity:node/1', TRUE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\UriInterface'), 'base://', TRUE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\UriInterface'), 'user-path:', TRUE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\UriInterface'), 'public://', TRUE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\UriInterface'), 'private://', TRUE];
+    $data[] = [$this->getMock('Drupal\Core\TypedData\Type\UriInterface'), 'drupal.org', FALSE];
+
+    return $data;
+  }
+
+}