diff --git a/PIL/GifImagePlugin.py b/PIL/GifImagePlugin.py
index 7fe662fc6..0b6f41648 100644
--- a/PIL/GifImagePlugin.py
+++ b/PIL/GifImagePlugin.py
@@ -298,7 +298,7 @@ except ImportError:
 RAWMODE = {
     "1": "L",
     "L": "L",
-    "P": "P",
+    "P": "P"
 }
 
 
@@ -321,7 +321,6 @@ def _save_all(im, fp, filename):
 
 
 def _save(im, fp, filename, save_all=False):
-
     im.encoderinfo.update(im.info)
     if _imaging_gif:
         # call external driver
@@ -344,62 +343,68 @@ def _save(im, fp, filename, save_all=False):
         im.encoderinfo["optimize"] = im.encoderinfo.get("optimize", True)
 
     if save_all:
-        previous = None
-
-        first_frame = None
-        append_images = im.encoderinfo.get("append_images", [])
+        # To specify duration, add the time in milliseconds to getdata(),
+        # e.g. getdata(im_frame, duration=1000)
         if "duration" in im.encoderinfo:
             duration = im.encoderinfo["duration"]
         else:
             duration = None
+        im_frames = []
+        append_images = im.encoderinfo.get("append_images", [])
         frame_count = 0
         for imSequence in [im]+append_images:
             for im_frame in ImageSequence.Iterator(imSequence):
-                encoderinfo = im.encoderinfo.copy()
                 im_frame = _convert_mode(im_frame)
+
+                encoderinfo = im.encoderinfo.copy()
                 if isinstance(duration, (list, tuple)):
-                    encoderinfo["duration"] = duration[frame_count]
+                    encoderinfo['duration'] = duration[frame_count]
                 frame_count += 1
 
-                # To specify duration, add the time in milliseconds to getdata(),
-                # e.g. getdata(im_frame, duration=1000)
-                if not previous:
-                    # global header
-                    first_frame = getheader(im_frame, palette, encoderinfo)[0]
-                    first_frame += getdata(im_frame, (0, 0), **encoderinfo)
-                else:
-                    if first_frame:
-                        for s in first_frame:
-                            fp.write(s)
-                        first_frame = None
-
+                if im_frames:
                     # delta frame
-                    delta = ImageChops.subtract_modulo(im_frame, previous.copy())
+                    previous = im_frames[-1]
+                    delta = ImageChops.subtract_modulo(im_frame,
+                                                       previous['im'])
                     bbox = delta.getbbox()
-
-                    if bbox:
-                        # compress difference
-                        encoderinfo['include_color_table'] = True
-                        for s in getdata(im_frame.crop(bbox),
-                                         bbox[:2], **encoderinfo):
-                            fp.write(s)
-                    else:
-                        # FIXME: what should we do in this case?
-                        pass
-                previous = im_frame
-        if first_frame:
+                    if not bbox:
+                        # This frame is identical to the previous frame
+                        if duration:
+                            previous['encoderinfo']['duration'] += encoderinfo['duration']
+                        continue
+                else:
+                    bbox = None
+                im_frames.append({
+                    'im':im_frame,
+                    'bbox':bbox,
+                    'encoderinfo':encoderinfo
+                })
+        if len(im_frames) < 2:
             save_all = False
+        else:
+            for frame_data in im_frames:
+                im_frame = frame_data['im']
+                if not frame_data['bbox']:
+                    # global header
+                    for s in getheader(im_frame, palette, frame_data['encoderinfo'])[0]:
+                        fp.write(s)
+                    offset = (0, 0)
+                else:
+                    # compress difference
+                    frame_data['encoderinfo']['include_color_table'] = True
+
+                    im_frame = im_frame.crop(frame_data['bbox'])
+                    offset = frame_data['bbox'][:2]
+                for s in getdata(im_frame, offset, **frame_data['encoderinfo']):
+                    fp.write(s)
     if not save_all:
-        header = getheader(im_out, palette, im.encoderinfo)[0]
-        for s in header:
+        for s in getheader(im_out, palette, im.encoderinfo)[0]:
             fp.write(s)
 
+        # local image header
         flags = 0
-
         if get_interlace(im):
             flags = flags | 64
-
-        # local image header
         _get_local_header(fp, im, (0, 0), flags)
 
         im_out.encoderconfig = (8, get_interlace(im))
diff --git a/Tests/test_file_gif.py b/Tests/test_file_gif.py
index d987f6851..df17efe8d 100644
--- a/Tests/test_file_gif.py
+++ b/Tests/test_file_gif.py
@@ -287,7 +287,7 @@ class TestFileGif(PillowTestCase):
         im_list = [
             Image.new('L', (100, 100), '#000'),
             Image.new('L', (100, 100), '#111'),
-            Image.new('L', (100, 100), '#222'),
+            Image.new('L', (100, 100), '#222')
         ]
 
         #duration as list
@@ -322,7 +322,31 @@ class TestFileGif(PillowTestCase):
             except EOFError:
                 pass
 
+    def test_identical_frames(self):
+        duration_list = [1000, 1500, 2000, 4000]
 
+        out = self.tempfile('temp.gif')
+        im_list = [
+            Image.new('L', (100, 100), '#000'),
+            Image.new('L', (100, 100), '#000'),
+            Image.new('L', (100, 100), '#000'),
+            Image.new('L', (100, 100), '#111')
+        ]
+
+        #duration as list
+        im_list[0].save(
+            out,
+            save_all=True,
+            append_images=im_list[1:],
+            duration=duration_list
+        )
+        reread = Image.open(out)
+
+        # Assert that the first three frames were combined
+        self.assertEqual(reread.n_frames, 2)
+
+        # Assert that the new duration is the total of the identical frames
+        self.assertEqual(reread.info['duration'], 4500)
 
     def test_number_of_loops(self):
         number_of_loops = 2
@@ -425,7 +449,7 @@ class TestFileGif(PillowTestCase):
         reloaded = Image.open(out)
 
         self.assertEqual(reloaded.info['transparency'], 253)
-        
+
 
 if __name__ == '__main__':
     unittest.main()