diff --git a/coffer-client/src/main.rs b/coffer-client/src/main.rs
index 6d215bd..cf70e73 100644
--- a/coffer-client/src/main.rs
+++ b/coffer-client/src/main.rs
@@ -5,7 +5,7 @@ use env_logger;
 use structopt::StructOpt;
 
 use std:: {
-    net::{SocketAddr, TcpStream},
+    net::TcpStream,
     error::Error,
     path::PathBuf,
     io::{Write, Read},
diff --git a/coffer-common/src/keyring.rs b/coffer-common/src/keyring.rs
index ec00547..87e50dd 100644
--- a/coffer-common/src/keyring.rs
+++ b/coffer-common/src/keyring.rs
@@ -44,7 +44,7 @@ pub struct Keyring {
 impl Keyring {
     pub fn new(certificate: Certificate) -> Keyring {
         Keyring {
-            certificate: certificate,
+            certificate,
             known_keys: HashMap::new()
         }
     }
diff --git a/coffer-companion/src/certificate.rs b/coffer-companion/src/certificate.rs
index 32f4826..f9a28ce 100644
--- a/coffer-companion/src/certificate.rs
+++ b/coffer-companion/src/certificate.rs
@@ -10,7 +10,7 @@ pub fn generate_key(out: PathBuf) {
     let cert = certificate.to_cbor().unwrap();
 
     let mut writer = File::create(&out)
-        .expect(&format!{"Could not create out file {}", &out.display()});
+        .unwrap_or_else(|_| panic!{"Could not create out file {}", &out.display()});
 
     writer.write_all(&cert).unwrap();
 }
diff --git a/coffer-server/src/coffer_map.rs b/coffer-server/src/coffer_map.rs
index 46acd8a..3941c71 100644
--- a/coffer-server/src/coffer_map.rs
+++ b/coffer-server/src/coffer_map.rs
@@ -7,7 +7,7 @@ use std::sync::RwLock;
 use std::sync::RwLockReadGuard;
 use std::sync::RwLockWriteGuard;
 
-use std::collections::HashMap;
+use std::collections::hash_map::{HashMap, Entry};
 
 use coffer_common::coffer::*;
 
@@ -34,8 +34,10 @@ impl Coffer for CofferMap {
 
         match lock.get_mut(&key.shard) {
             Some(shard) => {
-                if shard.contains_key(&key.key) { Err(CofferError::Msg("Key exists")) }
-                else { shard.insert(key.key, value); Ok(()) }
+                match shard.entry(key.key) {
+                    Entry::Occupied(_) => Err(CofferError::Msg("Key exists")),
+                    Entry::Vacant(v) => { v.insert(value); Ok(()) }
+                }
             }
             None => {
                 lock.insert(key.shard.clone(), HashMap::new());
diff --git a/coffer-server/src/server.rs b/coffer-server/src/server.rs
index 3139bcb..74dd5ef 100644
--- a/coffer-server/src/server.rs
+++ b/coffer-server/src/server.rs
@@ -59,7 +59,7 @@ where C: Coffer + Send + Sync + 'static
 
         debug!{"Binding to socket {:?}", socket}
         let mut listener = TcpListener::bind(socket).await
-            .expect(format!{"Could not bind to socket {}", socket}.as_str());
+            .expect("Could not bind to socket");
 
         let server = async move {
             let mut incoming = listener.incoming();