diff --git a/src/PIL/PngImagePlugin.py b/src/PIL/PngImagePlugin.py
index 442c65e6f..5a991b6e8 100644
--- a/src/PIL/PngImagePlugin.py
+++ b/src/PIL/PngImagePlugin.py
@@ -189,7 +189,7 @@ class ChunkStream:
         self.close()
 
     def close(self):
-        self.queue = self.crc = self.fp = None
+        self.queue = self.fp = None
 
     def push(self, cid, pos, length):