diff --git a/pkg/hs/urbit-king/lib/Urbit/King/CLI.hs b/pkg/hs/urbit-king/lib/Urbit/King/CLI.hs
index 4f91709a2f..5657ce8c8c 100644
--- a/pkg/hs/urbit-king/lib/Urbit/King/CLI.hs
+++ b/pkg/hs/urbit-king/lib/Urbit/King/CLI.hs
@@ -445,8 +445,8 @@ host = do
      ) <|>
      ( flag' NatWhenPrivateNetwork
      $ long "port-forwarding-when-internal"
-    <> help ("Try asking the router to forward when ip is 192.168.0.0/24 or" <>
-             "10.0.0.0/8 (default).")
+    <> help ("Try asking the router to forward when ip is 192.168.0.0/16, " <>
+             "172.16.0.0/12 or 10.0.0.0/8 (default).")
     <> hidden
      ) <|>
      (pure $ NatWhenPrivateNetwork)
diff --git a/pkg/hs/urbit-king/lib/Urbit/Vere/Ports.hs b/pkg/hs/urbit-king/lib/Urbit/Vere/Ports.hs
index bfb0ae61e9..18493b342b 100644
--- a/pkg/hs/urbit-king/lib/Urbit/Vere/Ports.hs
+++ b/pkg/hs/urbit-king/lib/Urbit/Vere/Ports.hs
@@ -104,6 +104,8 @@ portThread q stderr = do
     Left err -> do
       likelyIPAddress >>= \case
         Just ip@(192, 168, _, _) -> warnBehindRouterAndErr ip err
+        Just ip@(172, x, _, _)
+          | (x >= 16 && x <= 31) -> warnBehindRouterAndErr ip err
         Just ip@(10, _, _, _)    -> warnBehindRouterAndErr ip err
         _                        -> assumeOnPublicInternet
     Right pmp -> foundRouter pmp
@@ -245,6 +247,8 @@ likelyBehindRouter :: MonadIO m => m Bool
 likelyBehindRouter = do
   likelyIPAddress >>= \case
     Just ip@(192, 168, _, _) -> pure True
+    Just ip@(172, x, _, _)
+      | (x >= 16 && x <= 31) -> pure True
     Just ip@(10, _, _, _)    -> pure True
     _                        -> pure False