diff --git a/Tests/test_file_gif.py b/Tests/test_file_gif.py
index fa5d54feb..a03079ecd 100644
--- a/Tests/test_file_gif.py
+++ b/Tests/test_file_gif.py
@@ -856,7 +856,14 @@ def test_identical_frames(tmp_path):
 
 
 @pytest.mark.parametrize(
-    "duration", ([1000, 1500, 2000, 4000], (1000, 1500, 2000, 4000), 8500)
+    "duration",
+    (
+        [1000, 1500, 2000],
+        (1000, 1500, 2000),
+        # One more duration than the number of frames
+        [1000, 1500, 2000, 4000],
+        1500,
+    ),
 )
 def test_identical_frames_to_single_frame(duration, tmp_path):
     out = str(tmp_path / "temp.gif")
@@ -872,7 +879,7 @@ def test_identical_frames_to_single_frame(duration, tmp_path):
         assert reread.n_frames == 1
 
         # Assert that the new duration is the total of the identical frames
-        assert reread.info["duration"] == 8500
+        assert reread.info["duration"] == 4500
 
 
 def test_loop_none(tmp_path):
diff --git a/src/PIL/GifImagePlugin.py b/src/PIL/GifImagePlugin.py
index 4ce295f7f..799198598 100644
--- a/src/PIL/GifImagePlugin.py
+++ b/src/PIL/GifImagePlugin.py
@@ -627,28 +627,28 @@ def _write_multiple_frames(im, fp, palette):
                 bbox = None
             im_frames.append({"im": im_frame, "bbox": bbox, "encoderinfo": encoderinfo})
 
-    if len(im_frames) > 1:
-        for frame_data in im_frames:
-            im_frame = frame_data["im"]
-            if not frame_data["bbox"]:
-                # global header
-                for s in _get_global_header(im_frame, frame_data["encoderinfo"]):
-                    fp.write(s)
-                offset = (0, 0)
-            else:
-                # compress difference
-                if not palette:
-                    frame_data["encoderinfo"]["include_color_table"] = True
+    if len(im_frames) == 1:
+        if "duration" in im.encoderinfo:
+            # Since multiple frames will not be written, use the combined duration
+            im.encoderinfo["duration"] = im_frames[0]["encoderinfo"]["duration"]
+        return
 
-                im_frame = im_frame.crop(frame_data["bbox"])
-                offset = frame_data["bbox"][:2]
-            _write_frame_data(fp, im_frame, offset, frame_data["encoderinfo"])
-        return True
-    elif "duration" in im.encoderinfo and isinstance(
-        im.encoderinfo["duration"], (list, tuple)
-    ):
-        # Since multiple frames will not be written, add together the frame durations
-        im.encoderinfo["duration"] = sum(im.encoderinfo["duration"])
+    for frame_data in im_frames:
+        im_frame = frame_data["im"]
+        if not frame_data["bbox"]:
+            # global header
+            for s in _get_global_header(im_frame, frame_data["encoderinfo"]):
+                fp.write(s)
+            offset = (0, 0)
+        else:
+            # compress difference
+            if not palette:
+                frame_data["encoderinfo"]["include_color_table"] = True
+
+            im_frame = im_frame.crop(frame_data["bbox"])
+            offset = frame_data["bbox"][:2]
+        _write_frame_data(fp, im_frame, offset, frame_data["encoderinfo"])
+    return True
 
 
 def _save_all(im, fp, filename):