diff --git a/src/Intervention/Image/AbstractEncoder.php b/src/Intervention/Image/AbstractEncoder.php
index 66162a81..0b4e0638 100644
--- a/src/Intervention/Image/AbstractEncoder.php
+++ b/src/Intervention/Image/AbstractEncoder.php
@@ -62,13 +62,18 @@ abstract class AbstractEncoder
                 $this->result = $this->processPng();
                 break;
 
-            default:
             case 'jpg':
             case 'jpeg':
             case 'image/jpg':
             case 'image/jpeg':
                 $this->result = $this->processJpeg();
                 break;
+
+            default:
+                throw new \Intervention\Image\Exception\NotSupportedException(
+                    "Writing format ({$format}) is not supported."
+                );
+                break;
         }
 
         return $image->setEncoded($this->result);
@@ -83,7 +88,7 @@ abstract class AbstractEncoder
     {
         return sprintf('data:%s;base64,%s', 
             $this->image->mime, 
-            base64_encode($this->process($this->image, $this->quality))
+            base64_encode($this->process($this->image, null, $this->quality))
         );
     }
 
diff --git a/tests/EncoderTest.php b/tests/EncoderTest.php
index ac10c874..06de64f7 100644
--- a/tests/EncoderTest.php
+++ b/tests/EncoderTest.php
@@ -46,6 +46,31 @@ class EncoderTest extends PHPUnit_Framework_TestCase
         $this->assertEquals('image/gif; charset=binary', $this->getMime($encoder->result));
     }
 
+    public function testProcessUnknownWithMimeGd()
+    {
+        $core = imagecreatefromjpeg(__DIR__.'/images/test.jpg');
+        $encoder = new GdEncoder;
+        $image = Mockery::mock('\Intervention\Image\Image');
+        $image->mime = 'image/jpeg';
+        $image->shouldReceive('getCore')->once()->andReturn($core);
+        $image->shouldReceive('setEncoded')->once()->andReturn($image);
+        $img = $encoder->process($image, null);
+        $this->assertInstanceOf('Intervention\Image\Image', $img);
+        $this->assertEquals('image/jpeg; charset=binary', $this->getMime($encoder->result));
+    }
+
+    /**
+     * @expectedException \Intervention\Image\Exception\NotSupportedException
+     */
+    public function testProcessUnknownGd()
+    {
+        $core = imagecreatefromjpeg(__DIR__.'/images/test.jpg');
+        $encoder = new GdEncoder;
+        $image = Mockery::mock('\Intervention\Image\Image');
+        $img = $encoder->process($image, null);
+        $this->assertInstanceOf('Intervention\Image\Image', $img);
+    }
+
     public function testProcessJpegImagick()
     {
         $core = $this->getImagickMock('jpeg');
@@ -82,6 +107,30 @@ class EncoderTest extends PHPUnit_Framework_TestCase
         $this->assertEquals('mock-gif', $encoder->result);
     }
 
+    public function testProcessUnknownWithMimeImagick()
+    {
+        $core = $this->getImagickMock('jpeg');
+        $encoder = new ImagickEncoder;
+        $image = Mockery::mock('\Intervention\Image\Image');
+        $image->mime = 'image/jpeg';
+        $image->shouldReceive('getCore')->once()->andReturn($core);
+        $image->shouldReceive('setEncoded')->once()->andReturn($image);
+        $img = $encoder->process($image, null);
+        $this->assertInstanceOf('Intervention\Image\Image', $img);
+        $this->assertEquals('mock-jpeg', $encoder->result);
+    }
+
+    /**
+     * @expectedException \Intervention\Image\Exception\NotSupportedException
+     */
+    public function testProcessUnknownImagick()
+    {
+        $core = Mockery::mock('Imagick');
+        $encoder = new ImagickEncoder;
+        $image = Mockery::mock('\Intervention\Image\Image');
+        $img = $encoder->process($image, null);
+    }
+
     public function getImagickMock($type)
     {
         $imagick = Mockery::mock('Imagick');