diff --git a/Lib/xmlrpc/client.py b/Lib/xmlrpc/client.py
index 121fedf7f08..d18efce4c10 100644
--- a/Lib/xmlrpc/client.py
+++ b/Lib/xmlrpc/client.py
@@ -1203,7 +1203,7 @@ class Transport:
         headers = {}
         if extra_headers:
             for key, val in extra_headers:
-                header[key] = val
+                headers[key] = val
         headers["Content-Type"] = "text/xml"
         headers["User-Agent"] = self.user_agent
         connection.request("POST", handler, request_body, headers)
@@ -1271,7 +1271,7 @@ class SafeTransport(Transport):
         headers = {}
         if extra_headers:
             for key, val in extra_headers:
-                header[key] = val
+                headers[key] = val
         headers["Content-Type"] = "text/xml"
         headers["User-Agent"] = self.user_agent
         connection.request("POST", handler, request_body, headers)
diff --git a/Misc/NEWS b/Misc/NEWS
index 3d10f6ee55c..9c521f226ee 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -46,6 +46,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #3614: Corrected a typo in xmlrpc.client, leading to a NameError
+  "global name 'header' is not defined".
+
 - Issue #2834: update the regular expression library to match the unicode
   standards of py3k. In other words, mixing bytes and unicode strings
   (be it as pattern, search string or replacement string) raises a TypeError.