diff --git a/lib/ckb/indexer/api.rb b/lib/ckb/indexer/api.rb
index b393e97e..4432751f 100644
--- a/lib/ckb/indexer/api.rb
+++ b/lib/ckb/indexer/api.rb
@@ -6,7 +6,7 @@ class API
       attr_reader :rpc
       DEFAULT_LIMIT = 1000
 
-      def initialize(indexer_host, timeout_config = {})
+      def initialize(indexer_host = CKB::RPC::DEFAULT_INDEXER_URL, timeout_config = {})
         @rpc = CKB::RPC.new(host: indexer_host, timeout_config: timeout_config)
       end
 
diff --git a/lib/ckb/rpc.rb b/lib/ckb/rpc.rb
index 946ce80b..67f06cf7 100644
--- a/lib/ckb/rpc.rb
+++ b/lib/ckb/rpc.rb
@@ -25,6 +25,7 @@ class RPC
     attr_reader :uri, :http
 
     DEFAULT_URL = "http://localhost:8114"
+    DEFAULT_INDEXER_URL = "http://localhost:8116"
 
     def initialize(host: DEFAULT_URL, timeout_config: {})
       @uri = URI(host)