diff --git a/src/PIL/PngImagePlugin.py b/src/PIL/PngImagePlugin.py
index cd679d2c3..a91393726 100644
--- a/src/PIL/PngImagePlugin.py
+++ b/src/PIL/PngImagePlugin.py
@@ -1117,12 +1117,12 @@ def _write_multiple_frames(im, fp, chunk, rawmode):
                     and prev_disposal == encoderinfo.get("disposal")
                     and prev_blend == encoderinfo.get("blend")
                 ):
-                    now_duration = encoderinfo.get("duration", 0)
-                    if now_duration:
+                    frame_duration = encoderinfo.get("duration", 0)
+                    if frame_duration:
                         if "duration" in previous["encoderinfo"]:
-                            previous["encoderinfo"]["duration"] += now_duration
+                            previous["encoderinfo"]["duration"] += frame_duration
                         else:
-                            previous["encoderinfo"]["duration"] = now_duration
+                            previous["encoderinfo"]["duration"] = frame_duration
                     continue
             else:
                 bbox = None