Fixed the negative value check in io._BytesIO.seek().
diff --git a/Lib/io.py b/Lib/io.py
index 940c4c7..d85ed49 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -831,9 +831,9 @@
         except AttributeError as err:
             raise TypeError("an integer is required") from err
         if whence == 0:
-            self._pos = max(0, pos)
             if pos < 0:
                 raise ValueError("negative seek position %r" % (pos,))
+            self._pos = max(0, pos)
         elif whence == 1:
             self._pos = max(0, self._pos + pos)
         elif whence == 2: