diff --git a/requests/models.py b/requests/models.py
index 0f91b64e..b9a9d360 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -10,6 +10,11 @@ This module contains the primary objects that power Requests.
 import collections
 import datetime
 
+# Import encoding now, to avoid implicit import later.
+# Implicit import within threads may cause LookupError when standard library is in a ZIP,
+# such as in Embedded Python. See https://github.com/kennethreitz/requests/issues/3578.
+import encodings.idna
+
 from io import BytesIO, UnsupportedOperation
 from .hooks import default_hooks
 from .structures import CaseInsensitiveDict