diff --git a/tools/python/xen/xm/main.py b/tools/python/xen/xm/main.py
index ae3bc5a914..a460bc8a3a 100644
--- a/tools/python/xen/xm/main.py
+++ b/tools/python/xen/xm/main.py
@@ -2197,7 +2197,7 @@ def xm_pci_list_assignable_devices(args):
 
     devs =  server.xend.node.pciinfo()
  
-    fmt_str = "%(domain)04x:%(bus)02x:%(slot)02x:%(func)01x"
+    fmt_str = "%(domain)04x:%(bus)02x:%(slot)02x.%(func)01x"
     for x in devs:
         pci = parse_pci_info(x)
         print fmt_str % pci