diff --git a/nix/nixos-module/container/bird.nix b/nix/nixos-module/container/bird.nix
index aedbffa..17c3154 100644
--- a/nix/nixos-module/container/bird.nix
+++ b/nix/nixos-module/container/bird.nix
@@ -208,7 +208,9 @@ in
             ${text}
 
             # OSPFv2 to receive a default route from ${upstream}
-            protocol ospf v2 ZW4_${upstream} {
+            protocol ospf v2 ZW4_${
+              builtins.replaceStrings [ "-" ] [ "_" ] upstream
+            } {
               ipv4 {
                 import filter {
                   preference = preference + ${toString (100 - n)};
@@ -324,7 +326,9 @@ in
             ${text}
 
             # OSPFv3 to receive a default route from ${upstream}
-            protocol ospf v3 ZW6_${upstream} {
+            protocol ospf v3 ZW6_${
+              builtins.replaceStrings [ "-" ] [ "_" ] upstream
+            } {
               ipv6 {
                 import filter {
                   preference = preference + ${toString (100 - n)};