diff --git a/aiohttp/streams.py b/aiohttp/streams.py
index 7ac184391e6..82d404d617b 100644
--- a/aiohttp/streams.py
+++ b/aiohttp/streams.py
@@ -502,8 +502,9 @@ def _read_nowait_chunk(self, n: int) -> bytes:
         else:
             data = self._buffer.popleft()
 
-        self._size -= len(data)
-        self._cursor += len(data)
+        data_len = len(data)
+        self._size -= data_len
+        self._cursor += data_len
 
         chunk_splits = self._http_chunk_splits
         # Prevent memory leak: drop useless chunk splits