diff --git a/Cargo.toml b/Cargo.toml
index 860b2a8dca..9a41922bf6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -26,7 +26,6 @@ futures-util = { version = "0.3", default-features = false }
 http = "0.2"
 http-body = "=1.0.0-rc.2"
 pin-project-lite = "0.2.4"
-tokio = { version = "1.13", features = ["sync"] }
 
 # Optional
 
@@ -36,6 +35,7 @@ httparse = { version = "1.8", optional = true }
 httpdate = { version = "1.0", optional = true }
 itoa = { version = "1", optional = true }
 libc = { version = "0.2", optional = true }
+tokio = { version = "1", features = ["sync"], optional = true }
 tracing = { version = "0.1", default-features = false, features = ["std"], optional = true }
 want = { version = "0.3", optional = true }
 
@@ -74,13 +74,16 @@ full = [
 ]
 
 # HTTP versions
-http1 = ["dep:httparse", "dep:itoa"]
-http2 = ["dep:h2"]
+http1 = ["upgrade", "dep:httparse", "dep:itoa"]
+http2 = ["upgrade", "dep:h2"]
 
 # Client/Server
 client = ["dep:want"]
 server = ["dep:httpdate"]
 
+# HTTP Upgrades
+upgrade = ["dep:tokio"]
+
 # C-API support (currently unstable (no semver))
 ffi = ["dep:libc", "dep:http-body-util"]
 
diff --git a/src/common/io/mod.rs b/src/common/io/mod.rs
index 92f71c4ee6..3b886d4b99 100644
--- a/src/common/io/mod.rs
+++ b/src/common/io/mod.rs
@@ -1,7 +1,9 @@
 #[cfg(all(any(feature = "client", feature = "server"), feature = "http2"))]
 mod compat;
+#[cfg(feature = "upgrade")]
 mod rewind;
 
 #[cfg(all(any(feature = "client", feature = "server"), feature = "http2"))]
 pub(crate) use self::compat::{compat, Compat};
+#[cfg(feature = "upgrade")]
 pub(crate) use self::rewind::Rewind;
diff --git a/src/error.rs b/src/error.rs
index 719bd2a304..d9e08d0cce 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -48,6 +48,7 @@ pub(super) enum Kind {
     #[cfg(all(any(feature = "client", feature = "server"), feature = "http1"))]
     UnexpectedMessage,
     /// A pending item was dropped before ever being processed.
+    #[cfg(feature = "upgrade")]
     Canceled,
     /// Indicates a channel (client or body sender) is closed.
     ChannelClosed,
@@ -140,6 +141,7 @@ pub(super) enum User {
     UnsupportedStatusCode,
 
     /// User tried polling for an upgrade that doesn't exist.
+    #[cfg(feature = "upgrade")]
     NoUpgrade,
 
     /// User polled for an upgrade, but low-level API is not using upgrades.
@@ -186,6 +188,7 @@ impl Error {
     }
 
     /// Returns true if this was about a `Request` that was canceled.
+    #[cfg(feature = "upgrade")]
     pub fn is_canceled(&self) -> bool {
         matches!(self.inner.kind, Kind::Canceled)
     }
@@ -216,6 +219,7 @@ impl Error {
         }
     }
 
+    #[cfg(feature = "upgrade")]
     pub(super) fn with<C: Into<Cause>>(mut self, cause: C) -> Error {
         self.inner.cause = Some(cause.into());
         self
@@ -248,6 +252,7 @@ impl Error {
             .unwrap_or(h2::Reason::INTERNAL_ERROR)
     }
 
+    #[cfg(feature = "upgrade")]
     pub(super) fn new_canceled() -> Error {
         Error::new(Kind::Canceled)
     }
@@ -304,6 +309,7 @@ impl Error {
         Error::new(Kind::User(User::BodyWriteAborted))
     }
 
+    #[cfg(feature = "upgrade")]
     fn new_user(user: User) -> Error {
         Error::new(Kind::User(user))
     }
@@ -325,6 +331,7 @@ impl Error {
         Error::new_user(User::UnsupportedStatusCode)
     }
 
+    #[cfg(feature = "upgrade")]
     pub(super) fn new_user_no_upgrade() -> Error {
         Error::new_user(User::NoUpgrade)
     }
@@ -408,6 +415,7 @@ impl Error {
             #[cfg(all(any(feature = "client", feature = "server"), feature = "http1"))]
             Kind::UnexpectedMessage => "received unexpected message from connection",
             Kind::ChannelClosed => "channel closed",
+            #[cfg(feature = "upgrade")]
             Kind::Canceled => "operation was canceled",
             #[cfg(all(feature = "http1", feature = "server"))]
             Kind::HeaderTimeout => "read header from client timeout",
@@ -450,6 +458,7 @@ impl Error {
             Kind::User(User::UnsupportedStatusCode) => {
                 "response has 1xx status code, not supported by server"
             }
+            #[cfg(feature = "upgrade")]
             Kind::User(User::NoUpgrade) => "no upgrade available",
             #[cfg(all(any(feature = "client", feature = "server"), feature = "http1"))]
             Kind::User(User::ManualUpgrade) => "upgrade expected but low level API in use",
diff --git a/src/lib.rs b/src/lib.rs
index 0d1db8320a..c0ee66be35 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -49,8 +49,10 @@
 //! - `http2`: Enables HTTP/2 support.
 //! - `client`: Enables the HTTP `client`.
 //! - `server`: Enables the HTTP `server`.
+//! - `upgrade`: Enables [HTTP Upgrades].
 //!
 //! [feature flags]: https://doc.rust-lang.org/cargo/reference/manifest.html#the-features-section
+//! [Http Upgrades]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Protocol_upgrade_mechanism
 //!
 //! # Unstable Features
 //! hyper includes a set of unstable optional features that can be enabled through the use of a
@@ -93,7 +95,6 @@ pub mod ext;
 mod mock;
 pub mod rt;
 pub mod service;
-pub mod upgrade;
 
 #[cfg(feature = "ffi")]
 #[cfg_attr(docsrs, doc(cfg(all(feature = "ffi", hyper_unstable_ffi))))]
@@ -115,3 +116,9 @@ cfg_feature! {
 
     pub mod server;
 }
+
+cfg_feature! {
+    #![feature = "upgrade"]
+
+    pub mod upgrade;
+}
diff --git a/src/rt/io.rs b/src/rt/io.rs
index bf045c3714..059841b5cd 100644
--- a/src/rt/io.rs
+++ b/src/rt/io.rs
@@ -200,6 +200,7 @@ impl<'data> ReadBuf<'data> {
     }
 
     #[inline]
+    #[cfg(feature = "upgrade")]
     fn remaining(&self) -> usize {
         self.capacity() - self.filled
     }
@@ -244,11 +245,13 @@ impl<'data> ReadBufCursor<'data> {
     }
 
     #[inline]
+    #[cfg(feature = "upgrade")]
     pub(crate) fn remaining(&self) -> usize {
         self.buf.remaining()
     }
 
     #[inline]
+    #[cfg(feature = "upgrade")]
     pub(crate) fn put_slice(&mut self, buf: &[u8]) {
         assert!(
             self.buf.remaining() >= buf.len(),