diff --git a/modules/simpletest/tests/image.test b/modules/simpletest/tests/image.test
index 72090c6..cb346c1 100644
--- a/modules/simpletest/tests/image.test
+++ b/modules/simpletest/tests/image.test
@@ -334,13 +334,6 @@ class ImageToolkitGdTestCase extends DrupalWebTestCase {
     // Systems using non-bundled GD2 don't have imagerotate. Test if available.
     if (function_exists('imagerotate')) {
       $operations += array(
-        'rotate_5' => array(
-          'function' => 'rotate',
-          'arguments' => array(5, 0xFF00FF), // Fuchsia background.
-          'width' => 42,
-          'height' => 24,
-          'corners' => array_fill(0, 4, $this->fuchsia),
-        ),
         'rotate_90' => array(
           'function' => 'rotate',
           'arguments' => array(90, 0xFF00FF), // Fuchsia background.
@@ -348,13 +341,6 @@ class ImageToolkitGdTestCase extends DrupalWebTestCase {
           'height' => 40,
           'corners' => array($this->fuchsia, $this->red, $this->green, $this->blue),
         ),
-        'rotate_transparent_5' => array(
-          'function' => 'rotate',
-          'arguments' => array(5),
-          'width' => 42,
-          'height' => 24,
-          'corners' => array_fill(0, 4, $this->transparent),
-        ),
         'rotate_transparent_90' => array(
           'function' => 'rotate',
           'arguments' => array(90),
@@ -363,6 +349,49 @@ class ImageToolkitGdTestCase extends DrupalWebTestCase {
           'corners' => array($this->transparent, $this->red, $this->green, $this->blue),
         ),
       );
+      // As of PHP version 5.5, GD uses a different algorithm to rotate images
+      // than version 5.4 and below, resulting in different dimensions.
+      // See https://bugs.php.net/bug.php?id=65148).
+      // For the 40x20 test images, the dimensions resulting from rotation will
+      // be 1 pixel smaller in both width and height in PHP 5.5 and above.
+      // @todo: If and when the PHP bug gets solved, add an upper limit
+      //   version check.
+      if (version_compare(PHP_VERSION, '5.5', '>=')) {
+        $operations += array(
+          'rotate_5' => array(
+            'function' => 'rotate',
+            'arguments' => array(5, 0xFF00FF), // Fuchsia background.
+            'width' => 41,
+            'height' => 23,
+            'corners' => array_fill(0, 4, $this->fuchsia),
+          ),
+          'rotate_transparent_5' => array(
+            'function' => 'rotate',
+            'arguments' => array(5),
+            'width' => 41,
+            'height' => 23,
+            'corners' => array_fill(0, 4, $this->transparent),
+          ),
+        );
+      }
+      else {
+        $operations += array(
+          'rotate_5' => array(
+            'function' => 'rotate',
+            'arguments' => array(5, 0xFF00FF), // Fuchsia background.
+            'width' => 42,
+            'height' => 24,
+            'corners' => array_fill(0, 4, $this->fuchsia),
+          ),
+          'rotate_transparent_5' => array(
+            'function' => 'rotate',
+            'arguments' => array(5),
+            'width' => 42,
+            'height' => 24,
+            'corners' => array_fill(0, 4, $this->transparent),
+          ),
+        );
+      }
     }
 
     // Systems using non-bundled GD2 don't have imagefilter. Test if available.
@@ -419,17 +448,6 @@ class ImageToolkitGdTestCase extends DrupalWebTestCase {
         $correct_dimensions_object = TRUE;
         $correct_colors = TRUE;
 
-        // PHP 5.5 GD rotates differently than it did in PHP 5.4, resulting in
-        // different dimensions than what would normally be expected (see
-        // https://bugs.php.net/bug.php?id=65148). For the test images, the
-        // dimensions will be 1 pixel smaller in both dimensions (though other
-        // tests have shown a difference of 0 to 3 pixels in both dimensions).
-        // @todo: If and when the PHP bug gets solved, add an upper limit
-        //   version check.
-        if (version_compare(PHP_VERSION, '5.5', '>=') && $values['function'] === 'rotate' && $values['arguments'][0] % 90 != 0) {
-          $values['height']--;
-          $values['width']--;
-        }
         if (imagesy($image->resource) != $values['height'] || imagesx($image->resource) != $values['width']) {
           $correct_dimensions_real = FALSE;
         }
diff --git a/modules/system/image.gd.inc b/modules/system/image.gd.inc
index 5bd1625..6552a37 100644
--- a/modules/system/image.gd.inc
+++ b/modules/system/image.gd.inc
@@ -123,7 +123,7 @@ function image_gd_rotate(stdClass $image, $degrees, $background = NULL) {
 
   if (isset($background)) {
     $background = image_dec_to_rgba($background);
-    $background['alpha'] /= 2;
+    $background['alpha'] = 0;
   }
   else {
     // Background color is not specified: use transparent white as background.