diff --git a/Lib/xmlrpc/server.py b/Lib/xmlrpc/server.py
index 4ddc004..eb807c4 100644
--- a/Lib/xmlrpc/server.py
+++ b/Lib/xmlrpc/server.py
@@ -588,8 +588,12 @@
             self.handle_get()
         else:
             # POST data is normally available through stdin
+            try:
+                length = int(os.environ.get('CONTENT_LENGTH', None))
+            except ValueError:
+                length = -1
             if request_text is None:
-                request_text = sys.stdin.read()
+                request_text = sys.stdin.read(length)
 
             self.handle_xmlrpc(request_text)