diff --git a/src/Intervention/Image/Image.php b/src/Intervention/Image/Image.php
index b80d6294..7c0244a9 100644
--- a/src/Intervention/Image/Image.php
+++ b/src/Intervention/Image/Image.php
@@ -1283,12 +1283,11 @@ class Image
      * @param  integer $blue
      * @return Image
      */
-    public function colorize($red, $green, $blue, $alpha = 0)
+    public function colorize($red, $green, $blue)
     {
         if (($red < -100 || $red > 100) || 
             ($green < -100 || $green > 100) || 
-            ($blue < -100 || $blue > 100) || 
-            ($alpha < -100 || $alpha > 100)) {
+            ($blue < -100 || $blue > 100)) {
                 throw new Exception\ColorizeOutOfBoundsException(
                     'Colorize levels must be between -100 and +100'
             );
@@ -1298,10 +1297,9 @@ class Image
         $red = round($red * 2.55);
         $green = round($green * 2.55);
         $blue = round($blue * 2.55);
-        $alpha = round($alpha * 2.55);
 
         // apply filter
-        imagefilter($this->resource, IMG_FILTER_COLORIZE, $red, $green, $blue, $alpha);
+        imagefilter($this->resource, IMG_FILTER_COLORIZE, $red, $green, $blue);
 
         return $this;
     }
diff --git a/tests/ImageTest.php b/tests/ImageTest.php
index 3f11d327..88541ff6 100644
--- a/tests/ImageTest.php
+++ b/tests/ImageTest.php
@@ -1581,7 +1581,7 @@ class ImageTest extends PHPUnit_Framework_Testcase
     {
         $img = $this->getTestImage();
         $img->colorize(-100, 0, 100);
-        $img->colorize(100, -100, -100, 50);
+        $img->colorize(100, -100, -100);
         $this->assertInstanceOf('Intervention\Image\Image', $img);
     }