diff --git a/src/messenger/tests/webim/libs/MibewAPITest.php b/src/messenger/tests/webim/libs/MibewAPITest.php
index dc773b92..538ef97e 100644
--- a/src/messenger/tests/webim/libs/MibewAPITest.php
+++ b/src/messenger/tests/webim/libs/MibewAPITest.php
@@ -260,20 +260,6 @@ class MibewAPITest extends PHPUnit_Framework_TestCase {
 			);
 		}
 
-		// Wrong package. Signature element is empty.
-		$wrong_package = array('signature' => '');
-
-		// Try to catch MibewAPIException with MibewAPIException::EMPTY_SIGNATURE code
-		try {
-			$api->checkPackage($wrong_package, $trusted_signatures);
-			$this->fail("Exception must be thrown");
-		} catch (MibewAPIException $e) {
-			$this->assertEquals(
-				MibewAPIException::EMPTY_SIGNATURE,
-				$e->getCode()
-			);
-		}
-
 		// Wrong package. Signature is wrong.
 		$wrong_package = array('signature' => 'wrong_signature');
 
diff --git a/src/messenger/webim/libs/mibew_api.php b/src/messenger/webim/libs/mibew_api.php
index a8c00573..e8dd8f3c 100644
--- a/src/messenger/webim/libs/mibew_api.php
+++ b/src/messenger/webim/libs/mibew_api.php
@@ -67,7 +67,7 @@ Class MibewAPI {
 	 */
 	public function checkPackage($package, $trusted_signatures) {
 		// Check signature
-		if (empty($package['signature'])) {
+		if (! isset($package['signature'])) {
 			throw new MibewAPIException(
 				"Package signature is empty",
 				MibewAPIException::EMPTY_SIGNATURE
@@ -298,7 +298,7 @@ Class MibewAPI {
 						MibewAPIException::RESULT_FUNCTION_ALREADY_EXISTS
 					);
 				}
-				// Furst 'result' function found
+				// First 'result' function found
 				$result_function = $function;
 			}
 		}