diff --git a/src/configurable.rs b/src/configurable.rs
index 614a491d0..1f6734239 100644
--- a/src/configurable.rs
+++ b/src/configurable.rs
@@ -349,7 +349,7 @@ where
             self.a = Some(service);
         }
 
-        if let Async::Ready(service) = self.fut_b.poll().map_err(|e| e.into())? {
+        if let Async::Ready(service) = self.fut_b.poll()? {
             self.b = Some(service);
         }
 
diff --git a/src/lib.rs b/src/lib.rs
index 60533ff39..9293b9085 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -8,6 +8,14 @@
 //!
 // #![warn(missing_docs)]
 
+#![cfg_attr(
+    feature = "cargo-clippy",
+    allow(
+        declare_interior_mutable_const,
+        borrow_interior_mutable_const
+    )
+)]
+
 #[macro_use]
 extern crate log;
 extern crate bytes;
diff --git a/src/server.rs b/src/server.rs
index c80410054..43e67a689 100644
--- a/src/server.rs
+++ b/src/server.rs
@@ -1,5 +1,5 @@
 use std::time::Duration;
-use std::{fmt, io, mem, net};
+use std::{io, mem, net};
 
 use futures::sync::{mpsc, mpsc::unbounded};
 use futures::{Future, Sink, Stream};
@@ -150,7 +150,6 @@ impl Server {
         N: NewService<Request = TcpStream, Response = (), InitError = ()> + 'static,
         N::Service: 'static,
         N::Future: 'static,
-        N::Error: fmt::Display,
     {
         let sockets = bind_addr(addr)?;
 
@@ -167,7 +166,6 @@ impl Server {
         N: NewService<Request = TcpStream, Response = (), InitError = ()> + 'static,
         N::Service: 'static,
         N::Future: 'static,
-        N::Error: fmt::Display,
     {
         let token = Token(self.services.len());
         self.services.push(ServerNewService::create(factory));
diff --git a/src/server_service.rs b/src/server_service.rs
index 6debdbdb5..d597c5c08 100644
--- a/src/server_service.rs
+++ b/src/server_service.rs
@@ -1,7 +1,7 @@
 use std::cell::Cell;
+use std::net;
 use std::rc::Rc;
 use std::sync::atomic::{AtomicUsize, Ordering};
-use std::{fmt, net};
 
 use futures::future::{err, ok};
 use futures::task::AtomicTask;
@@ -64,7 +64,7 @@ impl<T> Service for ServerService<T>
 where
     T: Service<Request = TcpStream, Response = ()>,
     T::Future: 'static,
-    T::Error: fmt::Display + 'static,
+    T::Error: 'static,
 {
     type Request = ServerMessage;
     type Response = ();
@@ -117,7 +117,6 @@ where
     T: NewService<Request = TcpStream, Response = (), InitError = ()> + 'static,
     T::Service: 'static,
     T::Future: 'static,
-    T::Error: fmt::Display,
 {
     pub(crate) fn create(inner: F) -> Box<ServerServiceFactory + Send> {
         Box::new(Self { inner })
@@ -136,7 +135,6 @@ where
     T: NewService<Request = TcpStream, Response = (), InitError = ()> + 'static,
     T::Service: 'static,
     T::Future: 'static,
-    T::Error: fmt::Display,
 {
     fn clone_factory(&self) -> Box<ServerServiceFactory + Send> {
         Box::new(Self {
diff --git a/src/service/and_then.rs b/src/service/and_then.rs
index ef3a31146..922e10ed0 100644
--- a/src/service/and_then.rs
+++ b/src/service/and_then.rs
@@ -51,7 +51,7 @@ where
 
     fn poll_ready(&mut self) -> Poll<(), Self::Error> {
         match self.a.poll_ready() {
-            Ok(Async::Ready(_)) => self.b.borrow_mut().poll_ready().map_err(|e| e.into()),
+            Ok(Async::Ready(_)) => self.b.borrow_mut().poll_ready(),
             Ok(Async::NotReady) => Ok(Async::NotReady),
             Err(err) => Err(err),
         }
@@ -97,7 +97,7 @@ where
 
     fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
         if let Some(ref mut fut) = self.fut_b {
-            return fut.poll().map_err(|e| e.into());
+            return fut.poll();
         }
 
         match self.fut_a.poll() {
@@ -204,7 +204,7 @@ where
         }
 
         if self.b.is_none() {
-            if let Async::Ready(service) = self.fut_b.poll().map_err(|e| e.into())? {
+            if let Async::Ready(service) = self.fut_b.poll()? {
                 self.b = Some(service);
             }
         }