diff --git a/Cargo.toml b/Cargo.toml
index 0de0a1d4070b9eb0178722f50088942ceaba5809..560dfed03556515aef0ffd51febd75c3bc17ff9b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -15,6 +15,8 @@ license = "MIT OR Apache-2.0"
 
 readme = "README.md"
 
+edition = "2021"
+
 [dependencies]
 safemem = "0.3"
 memchr = "2.0"
diff --git a/src/lib.rs b/src/lib.rs
index 6a5365a0fd11f4d1a8b2c1e0c6ba9d6c0a2236bb..c5da85f9d630d9adc6bbd7e2945416e2411d6283 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -370,8 +370,8 @@ impl<R: Read, P> BufReader<R, P> {
     }
 
     /// Box the inner reader without losing data.
-    pub fn boxed<'a>(self) -> BufReader<Box<Read + 'a>, P> where R: 'a {
-        let inner: Box<Read + 'a> = Box::new(self.inner);
+    pub fn boxed<'a>(self) -> BufReader<Box<dyn Read + 'a>, P> where R: 'a {
+        let inner: Box<dyn Read> = Box::new(self.inner);
         
         BufReader {
             inner,
@@ -864,11 +864,7 @@ impl<W> Into<io::Error> for IntoInnerError<W> {
 }
 
 impl<W: Any + Send + fmt::Debug> error::Error for IntoInnerError<W> {
-    fn description(&self) -> &str {
-        error::Error::description(self.error())
-    }
-
-    fn cause(&self) -> Option<&error::Error> {
+    fn cause(&self) -> Option<&dyn error::Error> {
         Some(&self.1)
     }
 }
@@ -1047,7 +1043,7 @@ impl Buffer {
         }
 
         let read = {
-            let mut buf = unsafe { self.buf.write_buf() };
+            let buf = unsafe { self.buf.write_buf() };
             rdr.read(buf)?
         };
 
@@ -1065,7 +1061,7 @@ impl Buffer {
     /// space, this returns 0.
     pub fn copy_from_slice(&mut self, src: &[u8]) -> usize {
         let len = unsafe {
-            let mut buf = self.buf.write_buf();
+            let buf = self.buf.write_buf();
             let len = cmp::min(buf.len(), src.len());
             buf[..len].copy_from_slice(&src[..len]);
             len
@@ -1270,7 +1266,7 @@ pub fn copy_buf<B: BufRead, W: Write>(b: &mut B, w: &mut W) -> io::Result<u64> {
 }
 
 thread_local!(
-    static DROP_ERR_HANDLER: RefCell<Box<Fn(&mut Write, &mut Buffer, io::Error)>>
+    static DROP_ERR_HANDLER: RefCell<Box<dyn Fn(&mut dyn Write, &mut Buffer, io::Error)>>
         = RefCell::new(Box::new(|_, _, _| ()))
 );
 
@@ -1283,7 +1279,7 @@ thread_local!(
 /// ### Panics
 /// If called from within a handler previously provided to this function.
 pub fn set_drop_err_handler<F: 'static>(handler: F)
-where F: Fn(&mut Write, &mut Buffer, io::Error)
+where F: Fn(&mut dyn Write, &mut Buffer, io::Error)
 {
     DROP_ERR_HANDLER.with(|deh| *deh.borrow_mut() = Box::new(handler))
 }
diff --git a/src/policy.rs b/src/policy.rs
index c2ab54bf0411b1b98ca26a2f6d0123128e7c9024..a2fece62753978bfd69147a42edf6c6c40c9c760 100644
--- a/src/policy.rs
+++ b/src/policy.rs
@@ -22,8 +22,8 @@ pub struct DoRead(pub bool);
 /// Shorthand for `return DoRead(bool)` or `return DoRead(true)` (empty invocation)
 #[macro_export]
 macro_rules! do_read (
-    ($val:expr) => ( return $crate::policy::DoRead($val); );
-    () => ( do_read!(true); )
+    ($val:expr) => ( return $crate::policy::DoRead($val) );
+    () => ( do_read!(true) )
 );
 
 /// Default policy for both `BufReader` and `BufWriter` that reproduces the behaviors of their