diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 4b011e4..2b78549 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -693,7 +693,7 @@ def _use_posix_spawn():
 _USE_POSIX_SPAWN = _use_posix_spawn()
 
 
-class Popen(object):
+class Popen:
     """ Execute a child program in a new process.
 
     For a complete description of the arguments see the Python documentation.
@@ -844,6 +844,13 @@ def __init__(self, args, bufsize=-1, executable=None,
 
         self.text_mode = encoding or errors or text or universal_newlines
 
+        # PEP 597: We suppress the EncodingWarning in subprocess module
+        # for now (at Python 3.10), because we focus on files for now.
+        # This will be changed to encoding = io.text_encoding(encoding)
+        # in the future.
+        if self.text_mode and encoding is None:
+            self.encoding = encoding = "locale"
+
         # How long to resume waiting on a child after the first ^C.
         # There is no right value for this.  The purpose is to be polite
         # yet remain good for interactive users trying to exit a tool.