diff --git a/lib/private/User/Session.php b/lib/private/User/Session.php
index 4b56609ccf..a213ee48c2 100644
--- a/lib/private/User/Session.php
+++ b/lib/private/User/Session.php
@@ -362,6 +362,9 @@ class Session implements IUserSession, Emitter {
 		$user = $this->manager->get($username);
 		if (is_null($user)) {
 			$users = $this->manager->getByEmail($username);
+			if (empty($users)) {
+				return false;
+			}
 			if (count($users) !== 1) {
 				return true;
 			}
diff --git a/tests/lib/User/SessionTest.php b/tests/lib/User/SessionTest.php
index 21ac1b655b..614ed3d015 100644
--- a/tests/lib/User/SessionTest.php
+++ b/tests/lib/User/SessionTest.php
@@ -401,6 +401,32 @@ class SessionTest extends \Test\TestCase {
 		$userSession->logClientIn('john', 'doe', $request, $this->throttler);
 	}
 
+	public function testLogClientInUnexist() {
+		$manager = $this->getMockBuilder('\OC\User\Manager')
+			->disableOriginalConstructor()
+			->getMock();
+		$session = $this->createMock('\OCP\ISession');
+		$request = $this->createMock('\OCP\IRequest');
+		$user = $this->createMock('\OCP\IUser');
+
+		/** @var \OC\User\Session $userSession */
+		$userSession = $this->getMockBuilder('\OC\User\Session')
+			->setConstructorArgs([$manager, $session, $this->timeFactory, $this->tokenProvider, $this->config])
+			->setMethods(['login', 'supportsCookies', 'createSessionToken', 'getUser'])
+			->getMock();
+
+		$this->tokenProvider->expects($this->once())
+			->method('getToken')
+			->with('doe')
+			->will($this->throwException(new \OC\Authentication\Exceptions\InvalidTokenException()));
+		$this->config->expects($this->once())
+			->method('getSystemValue')
+			->with('token_auth_enforced', false)
+			->will($this->returnValue(false));
+
+		$this->assertFalse($userSession->logClientIn('unexist', 'doe', $request));
+	}
+
 	public function testLogClientInWithTokenPassword() {
 		$manager = $this->getMockBuilder('\OC\User\Manager')
 			->disableOriginalConstructor()