diff --git a/nodepool/nodepool.py b/nodepool/nodepool.py
index c972f1ed0..587ec92ee 100644
--- a/nodepool/nodepool.py
+++ b/nodepool/nodepool.py
@@ -288,7 +288,7 @@ class NodeLauncher(threading.Thread):
 
         ip = server.get('public_v4')
         if not ip and self.manager.hasExtension('os-floating-ips'):
-            ip = self.manager.addPublicIP(server['server_id'])
+            ip = self.manager.addPublicIP(server_id)
         if not ip:
             raise Exception("Unable to find public IP of server")