diff --git a/Tests/test_imageops_usm.py b/Tests/test_imageops_usm.py
index d417772c8..f6eae640b 100644
--- a/Tests/test_imageops_usm.py
+++ b/Tests/test_imageops_usm.py
@@ -60,9 +60,10 @@ class TestImageOpsUsm(PillowTestCase):
 
     def test_usm_accuracy(self):
 
-        i = snakes._new(ImageOps.unsharp_mask(snakes, 5, 1024, 0))
+        src = snakes.convert('RGB')
+        i = src._new(ImageOps.unsharp_mask(src, 5, 1024, 0))
         # Image should not be changed because it have only 0 and 255 levels.
-        self.assertEqual(i.tobytes(), snakes.tobytes())
+        self.assertEqual(i.tobytes(), src.tobytes())
 
     def test_blur_accuracy(self):
 
diff --git a/libImaging/UnsharpMask.c b/libImaging/UnsharpMask.c
index 61526cca7..ec3bb23cc 100644
--- a/libImaging/UnsharpMask.c
+++ b/libImaging/UnsharpMask.c
@@ -10,13 +10,16 @@
 #include "Imaging.h"
 
 
-static inline UINT8 clip(double in)
+typedef UINT8 pixel[4];
+
+
+static inline UINT8 clip8(int in)
 {
-    if (in >= 255.0)
-        return (UINT8) 255;
-    if (in <= 0.0)
-        return (UINT8) 0;
-    return (UINT8) (in + 0.5);
+    if (in >= 255)
+       return 255;
+    if (in <= 0)
+        return 0;
+    return (UINT8) in;
 }
 
 
@@ -25,109 +28,64 @@ ImagingUnsharpMask(Imaging imOut, Imaging imIn, float radius, int percent,
                    int threshold)
 {
     ImagingSectionCookie cookie;
-
     Imaging result;
-    int channel = 0;
-    int channels = 0;
-    int hasAlpha = 0;
 
-    int x = 0;
-    int y = 0;
+    int x, y, diff;
 
-    int *lineIn = NULL;
-    int *lineOut = NULL;
+    pixel *lineIn = NULL;
+    pixel *lineOut = NULL;
     UINT8 *lineIn8 = NULL;
     UINT8 *lineOut8 = NULL;
 
-    int diff = 0;
-
-    INT32 newPixel = 0;
-
-    if (strcmp(imIn->mode, "RGB") == 0) {
-        channels = 3;
-    } else if (strcmp(imIn->mode, "RGBA") == 0) {
-        channels = 3;
-    } else if (strcmp(imIn->mode, "RGBX") == 0) {
-        channels = 3;
-    } else if (strcmp(imIn->mode, "CMYK") == 0) {
-        channels = 4;
-    } else if (strcmp(imIn->mode, "L") == 0) {
-        channels = 1;
-    } else
-        return ImagingError_ModeError();
-
-    /* first, do a gaussian blur on the image, putting results in imOut
-       temporarily */
+    /* First, do a gaussian blur on the image, putting results in imOut
+       temporarily. All format checks are in gaussian blur. */
     result = ImagingGaussianBlur(imOut, imIn, radius, 3);
     if (!result)
         return NULL;
 
-    /* now, go through each pixel, compare "normal" pixel to blurred
-       pixel.  if the difference is more than threshold values, apply
+    /* Now, go through each pixel, compare "normal" pixel to blurred
+       pixel. If the difference is more than threshold values, apply
        the OPPOSITE correction to the amount of blur, multiplied by
        percent. */
 
     ImagingSectionEnter(&cookie);
 
-    if (strcmp(imIn->mode, "RGBX") == 0 || strcmp(imIn->mode, "RGBA") == 0) {
-        hasAlpha = 1;
-    }
-
     for (y = 0; y < imIn->ysize; y++) {
-        if (channels == 1) {
+        if (imIn->image8)
+        {
             lineIn8 = imIn->image8[y];
             lineOut8 = imOut->image8[y];
-        } else {
-            lineIn = imIn->image32[y];
-            lineOut = imOut->image32[y];
-        }
-        for (x = 0; x < imIn->xsize; x++) {
-            newPixel = 0;
-            /* compare in/out pixels, apply sharpening */
-            if (channels == 1) {
-                diff =
-                    ((UINT8 *) & lineIn8[x])[0] -
-                    ((UINT8 *) & lineOut8[x])[0];
+            for (x = 0; x < imIn->xsize; x++) {
+                /* compare in/out pixels, apply sharpening */
+                diff = lineIn8[x] - lineOut8[x];
                 if (abs(diff) > threshold) {
                     /* add the diff*percent to the original pixel */
-                    imOut->image8[y][x] =
-                        clip((((UINT8 *) & lineIn8[x])[0]) +
-                             (diff * ((float) percent) / 100.0));
+                    lineOut8[x] = clip8(lineIn8[x] + diff * percent / 100);
                 } else {
-                    /* newPixel is the same as imIn */
-                    imOut->image8[y][x] = ((UINT8 *) & lineIn8[x])[0];
+                    /* new pixel is the same as imIn */
+                    lineOut8[x] = lineIn8[x];
                 }
             }
+        } else {
+            lineIn = (pixel *)imIn->image32[y];
+            lineOut = (pixel *)imOut->image32[y];
+            for (x = 0; x < imIn->xsize; x++) {
+                /* compare in/out pixels, apply sharpening */
+                diff = lineIn[x][0] - lineOut[x][0];
+                lineOut[x][0] = abs(diff) > threshold ?
+                    clip8(lineIn[x][0] + diff * percent / 100) : lineIn[x][0];
 
-            else {
-                for (channel = 0; channel < channels; channel++) {
-                    diff = (int) ((((UINT8 *) & lineIn[x])[channel]) -
-                                  (((UINT8 *) & lineOut[x])[channel]));
-                    if (abs(diff) > threshold) {
-                        /* add the diff*percent to the original pixel
-                           this may not work for little-endian systems, fix it! */
-                        newPixel =
-                            newPixel |
-                            clip((float) (((UINT8 *) & lineIn[x])[channel])
-                                 +
-                                 (diff *
-                                  (((float) percent /
-                                    100.0)))) << (channel * 8);
-                    } else {
-                        /* newPixel is the same as imIn
-                           this may not work for little-endian systems, fix it! */
-                        newPixel =
-                            newPixel | ((UINT8 *) & lineIn[x])[channel] <<
-                            (channel * 8);
-                    }
-                }
-                if (hasAlpha) {
-                    /* preserve the alpha channel
-                       this may not work for little-endian systems, fix it! */
-                    newPixel =
-                        newPixel | ((UINT8 *) & lineIn[x])[channel] << 24;
-                }
-                imOut->image32[y][x] = newPixel;
+                diff = lineIn[x][1] - lineOut[x][1];
+                lineOut[x][1] = abs(diff) > threshold ?
+                    clip8(lineIn[x][1] + diff * percent / 100) : lineIn[x][1];
+
+                diff = lineIn[x][2] - lineOut[x][2];
+                lineOut[x][2] = abs(diff) > threshold ?
+                    clip8(lineIn[x][2] + diff * percent / 100) : lineIn[x][2];
+
+                diff = lineIn[x][3] - lineOut[x][3];
+                lineOut[x][3] = abs(diff) > threshold ?
+                    clip8(lineIn[x][3] + diff * percent / 100) : lineIn[x][3];
             }
         }
     }