diff --git a/PIL/BmpImagePlugin.py b/PIL/BmpImagePlugin.py
index 950ee13a1..eccd29923 100644
--- a/PIL/BmpImagePlugin.py
+++ b/PIL/BmpImagePlugin.py
@@ -112,7 +112,9 @@ class BmpImageFile(ImageFile.ImageFile):
                         # 40 byte headers only have the three components in the bitfields masks,
                         # ref: https://msdn.microsoft.com/en-us/library/windows/desktop/dd183376(v=vs.85).aspx
                         # See also https://github.com/python-pillow/Pillow/issues/1293
-                        file_info['a_mask'] = 0xff000000
+                        # There is a 4th component in the RGBQuad, in the alpha location, but it
+                        # is listed as a reserved component, and it is not generally an alpha channel
+                        file_info['a_mask'] = 0x0
                         for mask in ['r_mask', 'g_mask', 'b_mask']:
                             file_info[mask] = i32(read(4))
                     file_info['rgb_mask'] = (file_info['r_mask'], file_info['g_mask'], file_info['b_mask'])
diff --git a/Tests/test_file_bmp.py b/Tests/test_file_bmp.py
index 29d59ee44..1e373d037 100644
--- a/Tests/test_file_bmp.py
+++ b/Tests/test_file_bmp.py
@@ -74,8 +74,9 @@ class TestFileBmp(PillowTestCase):
         # test for #1293, Imagegrab returning Unsupported Bitfields Format
         im = BmpImagePlugin.DibImageFile('Tests/images/clipboard.dib')
         target = Image.open('Tests/images/clipboard_target.png')
+        # test only the RGB components, as there is no alpha in the DIB file. 
         self.assert_image_equal(im.convert('RGB'), target.convert('RGB'))
-        self.assert_image_similar(im, target, 1)
+
 
 
 if __name__ == '__main__':