diff --git a/Cargo.lock b/Cargo.lock
index f476540..d212ccd 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,7 +2,7 @@
 # It is not intended for manual editing.
 [[package]]
 name = "ace"
-version = "0.0.2"
+version = "0.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -540,7 +540,7 @@ dependencies = [
 
 [[package]]
 name = "tokio"
-version = "0.2.1"
+version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "bytes 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -578,13 +578,13 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "updns"
 version = "0.1.1"
 dependencies = [
- "ace 0.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ace 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "dirs 2.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 1.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.42 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -626,7 +626,7 @@ dependencies = [
 ]
 
 [metadata]
-"checksum ace 0.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "1e021d9548a20c4e74f88b5cff290ba225565e3404afcffdc6b275395128a140"
+"checksum ace 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "42d6302f03bbae8544fb07d9ab94bfbe2a5dbaadc857749d9fad959b55f13069"
 "checksum aho-corasick 0.7.6 (registry+https://github.com/rust-lang/crates.io-index)" = "58fb5e95d83b38284460a5fda7d6470aa0b8844d283a0b614b8535e880800d2d"
 "checksum arrayref 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" = "0d382e583f07208808f6b1249e60848879ba3543f57c32277bf52d69c2f0f0ee"
 "checksum arrayvec 0.4.11 (registry+https://github.com/rust-lang/crates.io-index)" = "b8d73f9beda665eaa98ab9e4f7442bd4e7de6652587de55b2525e52e29c1b0ba"
@@ -693,7 +693,7 @@ dependencies = [
 "checksum synstructure 0.10.2 (registry+https://github.com/rust-lang/crates.io-index)" = "02353edf96d6e4dc81aea2d8490a7e9db177bf8acb0e951c24940bf866cb313f"
 "checksum thread_local 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)" = "c6b53e329000edc2b34dbe8545fd20e55a333362d0a321909685a19bd28c3f1b"
 "checksum time 0.1.42 (registry+https://github.com/rust-lang/crates.io-index)" = "db8dcfca086c1143c9270ac42a2bbd8a7ee477b78ac8e45b19abfb0cbede4b6f"
-"checksum tokio 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "beeef686ef92a222de07e089f455d9f8478bbba9651718f9e4b276babe829082"
+"checksum tokio 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "2e765bf9f550bd9b8a970633ca3b56b8120c4b6c5dcbe26a93744cb02fee4b17"
 "checksum tokio-macros 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d5795a71419535c6dcecc9b6ca95bdd3c2d6142f7e8343d7beb9923f129aa87e"
 "checksum unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "fc72304796d0818e357ead4e000d19c9c174ab23dc11093ac919054d20a6a7fc"
 "checksum unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
diff --git a/Cargo.toml b/Cargo.toml
index 40d34df..141ecc9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -18,10 +18,10 @@ keywords = [
 ]
 
 [dependencies]
-ace = "0.0.2"
+ace = "0.0.3"
 dirs = "2.0.2"
 futures = "0.3.1"
 lazy_static = "1.4.0"
 regex = "1.3.1"
 time = "0.1.42"
-tokio = {version = "0.2.1", features = ["fs", "io-util",  "macros", "net", "stream", "time"]}
\ No newline at end of file
+tokio = {version = "0.2.2", features = ["fs", "io-util",  "macros", "net", "stream", "time"]}
\ No newline at end of file
diff --git a/src/config.rs b/src/config.rs
index 4090ee5..08ab7c6 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -80,6 +80,9 @@ impl Hosts {
 }
 
 // domain match
+const TEXT: &str = "abcdefghijklmnopqrstuvwxyz0123456789-.";
+const WILDCARD: &str = "abcdefghijklmnopqrstuvwxyz0123456789-.*";
+
 #[derive(Debug)]
 pub struct Host(MatchMode);
 
@@ -107,13 +110,11 @@ impl Host {
     }
 
     fn is_text(domain: &str) -> bool {
-        const ALLOW: &str = "abcdefghijklmnopqrstuvwxyz0123456789-.";
-        domain.chars().all(|item| ALLOW.chars().any(|c| item == c))
+        domain.chars().all(|item| TEXT.chars().any(|c| item == c))
     }
 
     fn is_wildcard(domain: &str) -> bool {
-        const ALLOW: &str = "abcdefghijklmnopqrstuvwxyz0123456789-.*";
-        domain.chars().all(|item| ALLOW.chars().any(|c| item == c))
+        domain.chars().all(|item| WILDCARD.chars().any(|c| item == c))
     }
 
     pub fn is_match(&self, domain: &str) -> bool {
diff --git a/src/watch.rs b/src/watch.rs
index c50ebe7..5f6faf4 100644
--- a/src/watch.rs
+++ b/src/watch.rs
@@ -40,10 +40,10 @@ impl Watch {
                 return true;
             }
         } else if a.is_err() && b.is_err() {
-            let left = a.as_ref().err().unwrap();
-            let right = b.as_ref().err().unwrap();
-            if left.kind() == right.kind() && left.raw_os_error() == right.raw_os_error() {
-                return true;
+            if let (Some(left), Some(right)) = (a.as_ref().err(), b.as_ref().err()) {
+                if left.kind() == right.kind() && left.raw_os_error() == right.raw_os_error() {
+                    return true;
+                }
             }
         }
         false