Index: library/Zend/File/Transfer/Adapter/Abstract.php
===================================================================
--- library/Zend/File/Transfer/Adapter/Abstract.php	(revision 19980)
+++ library/Zend/File/Transfer/Adapter/Abstract.php	(working copy)
@@ -1250,8 +1250,6 @@
             if (empty($result[$key])) {
                 if (function_exists('mime_content_type') && ini_get('mime_magic.magicfile')) {
                     $result[$key] = mime_content_type($file);
-                } else {
-                    $result[$key] = $value['type'];
                 }
             }
 
@@ -1511,4 +1509,5 @@
 
         return false;
     }
+
 }
Index: tests/Zend/File/Transfer/Adapter/_files/test.unknown
===================================================================
Index: tests/Zend/File/Transfer/Adapter/AbstractTest.php
===================================================================
--- tests/Zend/File/Transfer/Adapter/AbstractTest.php	(revision 19980)
+++ tests/Zend/File/Transfer/Adapter/AbstractTest.php	(working copy)
@@ -760,6 +760,16 @@
 
     public function testMimeTypeByTmpName()
     {
+        // this should throw an exception when the lookup functions are not present
+        if (!function_exists('mime_content_type') && !class_exists('finfo', false)) {
+            try {
+                $this->adapter->getMimeType('baz.text');
+                $this->fail('Exception was expected when lookup functions are not present.');
+            } catch (Exception $e) {
+                $this->assertContains('could not been detected', $e->getMessage());
+            }
+            return;
+        }
         $this->assertEquals('text/plain', $this->adapter->getMimeType('baz.text'));
     }
 
@@ -802,6 +812,16 @@
                 'bar' => array('magicFile' => 'test/file', 'ignoreNoFile' => false, 'useByteString' => true),
             ), $this->adapter->getOptions('bar'));
     }
+    
+    /**
+     * @group ZF-8733
+     * @expectedException Zend_File_Transfer_Exception
+     */
+    public function testMimeTypeThrowsExceptionWhenItDetectType()
+    {
+        $this->adapter->setValidFileUnknownExtension();
+        $this->adapter->getMimeType();
+    }
 }
 
 class Zend_File_Transfer_Adapter_AbstractTest_MockAdapter extends Zend_File_Transfer_Adapter_Abstract
@@ -932,6 +952,17 @@
             )
         );
     }
+    
+    public function setValidFileUnknownExtension()
+    {
+        $this->_files = array(
+            'test' => array(
+                'name'      => 'test.unknown',
+                'type'      => 'image/jpeg',
+                'tmp_name'  => dirname(__FILE__) . '/_files/test.unknown'
+                )
+            );
+    }
 }
 
 // Call Zend_File_Transfer_Adapter_AbstractTest::main() if this source file is executed directly.