diff --git a/server/routers/gerbil/getConfig.ts b/server/routers/gerbil/getConfig.ts
index b1f68e36..1eeb881c 100644
--- a/server/routers/gerbil/getConfig.ts
+++ b/server/routers/gerbil/getConfig.ts
@@ -124,7 +124,7 @@ async function getNextAvailableSubnet(): Promise<string> {
     }
 
     // replace the last octet with 1
-    subnet = subnet.split('.').slice(0, 3).join('.') + '.1' + subnet.split('/')[1];
+    subnet = subnet.split('.').slice(0, 3).join('.') + '.1' + '/' + subnet.split('/')[1];
     return subnet;
 }