diff --git a/src/Email.php b/src/Email.php
index 7acb4a7..f92f81b 100644
--- a/src/Email.php
+++ b/src/Email.php
@@ -23,7 +23,7 @@ public function __toString()
 
     private function ensureIsValidEmail(string $email)
     {
-        if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
+        if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
             throw new InvalidArgumentException(
                 sprintf(
                     '"%s" is not a valid email address',
diff --git a/tests/EmailTest.php b/tests/EmailTest.php
index 0b40386..75212db 100644
--- a/tests/EmailTest.php
+++ b/tests/EmailTest.php
@@ -31,6 +31,6 @@ public function testCanBeUsedAsString()
 
     public function testFail()
     {
-        $this->assertEquals(4,4);
+        $this->assertEquals(3,4);
     }
 }