diff --git a/acme_common/src/crypto/openssl_certificate.rs b/acme_common/src/crypto/openssl_certificate.rs
index 87a760d..24eaf23 100644
--- a/acme_common/src/crypto/openssl_certificate.rs
+++ b/acme_common/src/crypto/openssl_certificate.rs
@@ -72,7 +72,7 @@ impl X509Certificate {
         crt.tbs_certificate
             .validity
             .time_to_expiration()
-            .ok_or(Error::from("Invalid certificate validity."))
+            .ok_or_else(|| Error::from("Invalid certificate validity."))
     }
 
     pub fn subject_alt_names(&self) -> HashSet<String> {
diff --git a/acmed/build.rs b/acmed/build.rs
index 745d83d..bd0b419 100644
--- a/acmed/build.rs
+++ b/acmed/build.rs
@@ -69,7 +69,7 @@ fn set_lock() {
 }
 
 fn get_openssl_version_unit(n: u64, pos: u32) -> u64 {
-    let p = 0xff_00_00_00_0 >> (8 * pos);
+    let p = 0x000f_f000_0000 >> (8 * pos);
     let n = n & p;
     n >> (8 * (3 - pos) + 4)
 }
@@ -118,7 +118,7 @@ fn set_tls() {
         set_rustc_env_var!("ACMED_TLS_LIB_VERSION", version);
         set_rustc_env_var!("ACMED_TLS_LIB_NAME", "LibreSSL");
     }
-    if let Ok(_) = env::var("CARGO_FEATURE_STANDALONE") {
+    if env::var("CARGO_FEATURE_STANDALONE").is_ok() {
         let version = get_lib_version("ring").unwrap();
         set_rustc_env_var!("ACMED_TLS_LIB_VERSION", version);
         set_rustc_env_var!("ACMED_TLS_LIB_NAME", "ring");
diff --git a/acmed/src/acme_proto/http.rs b/acmed/src/acme_proto/http.rs
index 4aa7ac7..ff19ead 100644
--- a/acmed/src/acme_proto/http.rs
+++ b/acmed/src/acme_proto/http.rs
@@ -100,7 +100,7 @@ fn nonce_from_response(cert: &Certificate, res: &Response) -> Result<String, Err
     let nonce = get_header(res, "Replay-Nonce")?;
     if is_nonce(&nonce) {
         cert.trace(&format!("New nonce: {}", nonce));
-        Ok(nonce.to_string())
+        Ok(nonce)
     } else {
         let msg = format!("{}: invalid nonce.", nonce);
         Err(msg.into())
@@ -123,13 +123,13 @@ fn post_jose_type(
     let rstr = String::from_utf8_lossy(data);
     cert.trace(&format!("request body: {}", rstr));
     let (res, res_body) = send_request(cert, &request)?;
-    let lpos = res_body.find("{").unwrap_or(0);
+    let lpos = res_body.find('{').unwrap_or(0);
     let res_body = if lpos == 0 {
         res_body
     } else {
         res_body.chars().skip(lpos).collect::<String>()
     };
-    let rpos = res_body.rfind("}").unwrap_or(0);
+    let rpos = res_body.rfind('}').unwrap_or(0);
     let res_body = if rpos == 0 {
         res_body
     } else {
diff --git a/acmed/src/certificate.rs b/acmed/src/certificate.rs
index d5ca601..b871100 100644
--- a/acmed/src/certificate.rs
+++ b/acmed/src/certificate.rs
@@ -108,7 +108,7 @@ impl Certificate {
         self.debug(&format!("expires in {} days", expires_in.as_secs() / 86400));
         // TODO: allow a custom duration (using time-parse ?)
         // 1814400 is 3 weeks (3 * 7 * 24 * 60 * 60)
-        let renewal_time = Duration::new(1814400, 0);
+        let renewal_time = Duration::new(1_814_400, 0);
         Ok(expires_in <= renewal_time)
     }
 
diff --git a/acmed/src/config.rs b/acmed/src/config.rs
index 8aba14f..b1b9846 100644
--- a/acmed/src/config.rs
+++ b/acmed/src/config.rs
@@ -300,7 +300,8 @@ impl Certificate {
         match &self.name {
             Some(n) => n.to_string(),
             None => self.domains.first().unwrap().dns.to_owned(),
-        }.replace("*", "_")
+        }
+        .replace("*", "_")
     }
 
     pub fn get_crt_name_format(&self) -> String {
diff --git a/acmed/src/main_event_loop.rs b/acmed/src/main_event_loop.rs
index db90fab..3ac39b7 100644
--- a/acmed/src/main_event_loop.rs
+++ b/acmed/src/main_event_loop.rs
@@ -74,7 +74,7 @@ impl MainEventLoop {
 
         Ok(MainEventLoop {
             certs,
-            root_certs: root_certs.iter().map(|v| v.to_string()).collect(),
+            root_certs: root_certs.iter().map(|v| (*v).to_string()).collect(),
         })
     }