diff --git a/tools/ui/Cargo.lock b/tools/ui/Cargo.lock
index 43aceb40..1b28c78d 100644
--- a/tools/ui/Cargo.lock
+++ b/tools/ui/Cargo.lock
@@ -117,7 +117,7 @@ checksum = "1fd0f2584146f6f2ef48085050886acf353beff7305ebd1ae69500e27c67f64b"
 
 [[package]]
 name = "candid"
-version = "0.10.0"
+version = "0.10.2"
 dependencies = [
  "anyhow",
  "binread",
@@ -415,14 +415,12 @@ checksum = "a54b5297861c651551676e8c43df805dad175cc33bc97dbd992edbbb85dcbcdf"
 
 [[package]]
 name = "ic_principal"
-version = "0.1.0"
+version = "0.1.1"
 dependencies = [
  "arbitrary",
  "crc32fast",
  "data-encoding",
- "hex",
  "serde",
- "serde_bytes",
  "sha2",
  "thiserror",
 ]
diff --git a/tools/ui/src/candid.ts b/tools/ui/src/candid.ts
index bbba1cda..24f5f7f9 100644
--- a/tools/ui/src/candid.ts
+++ b/tools/ui/src/candid.ts
@@ -12,16 +12,18 @@ declare var d3: any;
 
 const names: Record<number,string> = {};
 
-function is_local(agent: HttpAgent) {
+function isKnownMainnet(agent: HttpAgent) {
   // @ts-ignore
   const hostname = agent._host.hostname;
-  return hostname === '127.0.0.1' || hostname.endsWith('localhost');
+  return hostname.endsWith('.icp0.io') || hostname.endsWith('.ic0.app');
 }
 
 export let authClient: AuthClient | undefined;
 
-const agent = new HttpAgent();
-if (is_local(agent)) {
+const agent = new HttpAgent({
+  host: window.location.host.replace(/^(localhost)(:\d+)?$/, '127.0.0.1$2')
+});
+if (!isKnownMainnet(agent)) {
   agent.fetchRootKey();
 }