diff --git a/src/backend/mod.rs b/src/backend/mod.rs
index fd0b60d..0cc037e 100644
--- a/src/backend/mod.rs
+++ b/src/backend/mod.rs
@@ -17,7 +17,8 @@ use tokio_rustls::rustls::{
 pub use upstream::{ReverseProxy, Upstream, UpstreamGroup};
 pub use upstream_opts::UpstreamOption;
 
-// server name (hostname or ip address) and path name representation in backends
+// Server name (hostname or ip address) and path name representation in backends
+// For searching hashmap or key list by exact or longest-prefix matching
 pub type ServerNameExp = Vec<u8>; // lowercase ascii bytes
 pub type PathNameExp = Vec<u8>; // lowercase ascii bytes
 
@@ -111,7 +112,7 @@ impl Backend {
 /// HashMap and some meta information for multiple Backend structs.
 pub struct Backends {
   pub apps: HashMap<ServerNameExp, Backend>, // hyper::uriで抜いたhostで引っ掛ける
-  pub default_server_name: Option<ServerNameExp>, // for plaintext http
+  pub default_server_name_bytes: Option<ServerNameExp>, // for plaintext http
 }
 
 impl Backends {
diff --git a/src/config/parse.rs b/src/config/parse.rs
index 19b080f..7be29ee 100644
--- a/src/config/parse.rs
+++ b/src/config/parse.rs
@@ -150,7 +150,7 @@ pub fn parse_opts(globals: &mut Globals) -> std::result::Result<(), anyhow::Erro
         "Serving plaintext http for requests to unconfigured server_name by app {} (server_name: {}).",
         d, d_sn[0]
       );
-      globals.backends.default_server_name = Some(d_sn[0].as_bytes().to_vec());
+      globals.backends.default_server_name_bytes = Some(d_sn[0].as_bytes().to_vec());
     }
   }
 
diff --git a/src/handler/handler_main.rs b/src/handler/handler_main.rs
index 045b190..f371cf8 100644
--- a/src/handler/handler_main.rs
+++ b/src/handler/handler_main.rs
@@ -62,7 +62,7 @@ where
     // Find backend application for given server_name, and drop if incoming request is invalid as request.
     let backend = if let Some(be) = self.globals.backends.apps.get(&server_name_bytes) {
       be
-    } else if let Some(default_server_name) = &self.globals.backends.default_server_name {
+    } else if let Some(default_server_name) = &self.globals.backends.default_server_name_bytes {
       debug!("Serving by default app");
       self.globals.backends.apps.get(default_server_name).unwrap()
     } else {
diff --git a/src/main.rs b/src/main.rs
index b69acd6..32703a2 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -71,7 +71,7 @@ fn main() {
 
       runtime_handle: runtime.handle().clone(),
       backends: Backends {
-        default_server_name: None,
+        default_server_name_bytes: None,
         apps: HashMap::<ServerNameExp, Backend>::default(),
       },