diff --git a/Tools/demo/rpython.py b/Tools/demo/rpython.py
index 5e7bc0a27d1..71d436c46db 100755
--- a/Tools/demo/rpython.py
+++ b/Tools/demo/rpython.py
@@ -19,7 +19,7 @@ def main():
     port = PORT
     i = host.find(':')
     if i >= 0:
-        port = int(port[i+1:])
+        port = int(host[i+1:])
         host = host[:i]
     command = ' '.join(sys.argv[2:])
     s = socket(AF_INET, SOCK_STREAM)