diff --git a/lib/private/appframework/http/request.php b/lib/private/appframework/http/request.php
index 96620838dfb..8400882b88f 100644
--- a/lib/private/appframework/http/request.php
+++ b/lib/private/appframework/http/request.php
@@ -674,6 +674,9 @@ class Request implements \ArrayAccess, \Countable, IRequest {
 	 * @return bool true if at least one of the given agent matches, false otherwise
 	 */
 	public function isUserAgent(array $agent) {
+		if (!isset($this->server['HTTP_USER_AGENT'])) {
+			return false;
+		}
 		foreach ($agent as $regex) {
 			if (preg_match($regex, $this->server['HTTP_USER_AGENT'])) {
 				return true;
diff --git a/tests/lib/appframework/http/RequestTest.php b/tests/lib/appframework/http/RequestTest.php
index f628a30f1da..ab5fe154441 100644
--- a/tests/lib/appframework/http/RequestTest.php
+++ b/tests/lib/appframework/http/RequestTest.php
@@ -693,19 +693,36 @@ class RequestTest extends \Test\TestCase {
 	 */
 	public function testUserAgent($testAgent, $userAgent, $matches) {
 		$request = new Request(
-			[
-				'server' => [
-					'HTTP_USER_AGENT' => $testAgent,
-				]
-			],
-			$this->secureRandom,
-			$this->config,
-			$this->stream
+				[
+						'server' => [
+								'HTTP_USER_AGENT' => $testAgent,
+						]
+				],
+				$this->secureRandom,
+				$this->config,
+				$this->stream
 		);
 
 		$this->assertSame($matches, $request->isUserAgent($userAgent));
 	}
 
+	/**
+	 * @dataProvider userAgentProvider
+	 * @param string $testAgent
+	 * @param array $userAgent
+	 * @param bool $matches
+	 */
+	public function testUndefinedUserAgent($testAgent, $userAgent, $matches) {
+		$request = new Request(
+				[],
+				$this->secureRandom,
+				$this->config,
+				$this->stream
+		);
+
+		$this->assertFalse($request->isUserAgent($userAgent));
+	}
+
 	/**
 	 * @return array
 	 */