diff --git a/Lib/email/mime/text.py b/Lib/email/mime/text.py
index 87de8d235f9..35b44238300 100644
--- a/Lib/email/mime/text.py
+++ b/Lib/email/mime/text.py
@@ -35,10 +35,8 @@ class MIMEText(MIMENonMultipart):
                 _charset = 'us-ascii'
             except UnicodeEncodeError:
                 _charset = 'utf-8'
-        if isinstance(_charset, Charset):
-            _charset = str(_charset)
 
         MIMENonMultipart.__init__(self, 'text', _subtype, policy=policy,
-                                  **{'charset': _charset})
+                                  **{'charset': str(_charset)})
 
         self.set_payload(_text, _charset)
diff --git a/Lib/test/test_email/test_email.py b/Lib/test/test_email/test_email.py
index 30ea77f2080..529d3ef0e3d 100644
--- a/Lib/test/test_email/test_email.py
+++ b/Lib/test/test_email/test_email.py
@@ -1653,9 +1653,12 @@ class TestMIMEText(unittest.TestCase):
         eq(msg.get_charset().input_charset, 'us-ascii')
         eq(msg['content-type'], 'text/plain; charset="us-ascii"')
         # Also accept a Charset instance
-        msg = MIMEText('hello there', _charset=Charset('utf-8'))
+        charset = Charset('utf-8')
+        charset.body_encoding = None
+        msg = MIMEText('hello there', _charset=charset)
         eq(msg.get_charset().input_charset, 'utf-8')
         eq(msg['content-type'], 'text/plain; charset="utf-8"')
+        eq(msg.get_payload(), 'hello there')
 
     def test_7bit_input(self):
         eq = self.assertEqual
diff --git a/Misc/NEWS b/Misc/NEWS
index 1fc6d638f37..b03e3d54558 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -92,6 +92,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #27445: Don't pass str(_charset) to MIMEText.set_payload().
+  Patch by Claude Paroz.
+
 - Issue #24277: The new email API is no longer provisional, and the docs
   have been reorganized and rewritten to emphasize the new API.