diff --git a/lib/Doctrine/Common/Persistence/Mapping/AbstractClassMetadataFactory.php b/lib/Doctrine/Common/Persistence/Mapping/AbstractClassMetadataFactory.php
index 586b2da2c..cba424b06 100644
--- a/lib/Doctrine/Common/Persistence/Mapping/AbstractClassMetadataFactory.php
+++ b/lib/Doctrine/Common/Persistence/Mapping/AbstractClassMetadataFactory.php
@@ -208,7 +208,7 @@ public function getMetadataFor($className)
 
         try {
             if ($this->cacheDriver) {
-                if (($cached = $this->cacheDriver->fetch($realClassName . $this->cacheSalt)) !== false) {
+                if (($cached = $this->cacheDriver->fetch($realClassName . $this->cacheSalt)) instanceof ClassMetadata) {
                     $this->loadedMetadata[$realClassName] = $cached;
 
                     $this->wakeupReflection($cached, $this->getReflectionService());
diff --git a/tests/Doctrine/Tests/Common/Persistence/Mapping/ClassMetadataFactoryTest.php b/tests/Doctrine/Tests/Common/Persistence/Mapping/ClassMetadataFactoryTest.php
index 0b0a3e4af..ddcdce480 100644
--- a/tests/Doctrine/Tests/Common/Persistence/Mapping/ClassMetadataFactoryTest.php
+++ b/tests/Doctrine/Tests/Common/Persistence/Mapping/ClassMetadataFactoryTest.php
@@ -2,6 +2,7 @@
 
 namespace Doctrine\Tests\Common\Persistence\Mapping;
 
+use Doctrine\Common\Cache\Cache;
 use Doctrine\Common\Persistence\Mapping\Driver\MappingDriver;
 use Doctrine\Common\Persistence\Mapping\MappingException;
 use Doctrine\Tests\DoctrineTestCase;
@@ -10,6 +11,9 @@
 use Doctrine\Common\Persistence\Mapping\AbstractClassMetadataFactory;
 use Doctrine\Common\Cache\ArrayCache;
 
+/**
+ * @covers \Doctrine\Common\Persistence\Mapping\AbstractClassMetadataFactory
+ */
 class ClassMetadataFactoryTest extends DoctrineTestCase
 {
     /**
@@ -130,6 +134,30 @@ public function testWillFailOnFallbackFailureWithNotLoadedMetadata()
 
         $this->cmf->getMetadataFor('Foo');
     }
+
+    /**
+     * @group 717
+     */
+    public function testWillIgnoreCacheEntriesThatAreNotMetadataInstances()
+    {
+        /* @var $cacheDriver Cache|\PHPUnit_Framework_MockObject_MockObject */
+        $cacheDriver = $this->createMock(Cache::class);
+
+        $this->cmf->setCacheDriver($cacheDriver);
+
+        $cacheDriver->expects(self::once())->method('fetch')->with('Foo$CLASSMETADATA')->willReturn(new \stdClass());
+
+        /* @var $metadata ClassMetadata */
+        $metadata = $this->createMock(ClassMetadata::class);
+
+        $fallbackCallback = $this->getMockBuilder(\stdClass::class)->setMethods(['__invoke'])->getMock();
+
+        $fallbackCallback->expects(self::any())->method('__invoke')->willReturn($metadata);
+
+        $this->cmf->fallbackCallback = $fallbackCallback;
+
+        self::assertSame($metadata, $this->cmf->getMetadataFor('Foo'));
+    }
 }
 
 class TestClassMetadataFactory extends AbstractClassMetadataFactory