diff --git a/src/firewall/core/nftables.py b/src/firewall/core/nftables.py
index a9d5a45..69ee63b 100644
--- a/src/firewall/core/nftables.py
+++ b/src/firewall/core/nftables.py
@@ -1680,7 +1680,7 @@ class nftables(object):
                     port_str = entry_tokens[i][index+1:]
 
                 try:
-                    index = entry_tokens[i].index("-")
+                    index = port_str.index("-")
                 except ValueError:
                     fragment.append(port_str)
                 else: