1 files changed, 3 insertions, 0 deletions
diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index a188393f79..dfdbdecb80 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -1048,6 +1048,9 @@ class AbstractHTTPHandler(BaseHandler):
 
         if request.data is not None:  # POST
             data = request.data
+            if isinstance(data, str):
+                raise TypeError("POST data should be bytes"
+                        " or an iterable of bytes. It cannot be str.")
             if not request.has_header('Content-type'):
                 request.add_unredirected_header(
                     'Content-type',