diff --git a/Cargo.toml b/Cargo.toml
index f147404..766c740 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -30,8 +30,8 @@ async-task = "1.0.0"
 cfg-if = "0.1.9"
 crossbeam-channel = "0.3.9"
 crossbeam-deque = "0.7.1"
-futures-core-preview = "=0.3.0-alpha.18"
-futures-io-preview = "=0.3.0-alpha.18"
+futures-core-preview = "=0.3.0-alpha.19"
+futures-io-preview = "=0.3.0-alpha.19"
 futures-timer = "0.4.0"
 lazy_static = "1.4.0"
 log = { version = "0.4.8", features = ["kv_unstable"] }
@@ -48,11 +48,11 @@ broadcaster = { version = "0.2.6", optional = true, default-features = false, fe
 femme = "1.2.0"
 surf = "1.0.2"
 tempdir = "0.3.7"
+futures-preview = { version = "=0.3.0-alpha.19", features = ["async-await"] }
 
 # These are used by the book for examples
-futures-channel-preview = "=0.3.0-alpha.18"
-futures-util-preview = "=0.3.0-alpha.18"
+futures-channel-preview = "=0.3.0-alpha.19"
+futures-util-preview = "=0.3.0-alpha.19"
 
-[dev-dependencies.futures-preview]
-version = "=0.3.0-alpha.18"
-features = ["std", "nightly", "async-await"]
+[patch.crates-io]
+surf = { git = "https://github.com/taiki-e/surf", branch = "futures" }
diff --git a/docs/src/tutorial/specification.md b/docs/src/tutorial/specification.md
index ce2abcb..bda4576 100644
--- a/docs/src/tutorial/specification.md
+++ b/docs/src/tutorial/specification.md
@@ -50,6 +50,6 @@ Add the following lines to `Cargo.toml`:
 
 ```toml
 [dependencies]
-futures-preview = { version = "0.3.0-alpha.18", features = [ "async-await", "nightly" ] }
+futures-preview = { version = "0.3.0-alpha.19", features = [ "async-await" ] }
 async-std = "0.99"
 ```
diff --git a/src/io/read/mod.rs b/src/io/read/mod.rs
index 9c81f95..6fd95c1 100644
--- a/src/io/read/mod.rs
+++ b/src/io/read/mod.rs
@@ -461,6 +461,15 @@ extension_trait! {
     }
 }
 
+/// Initializes a buffer if necessary.
+///
+/// Currently, a buffer is always initialized because `read_initializer`
+/// feature is not stable.
+#[inline]
+unsafe fn initialize<R: futures_io::AsyncRead>(_reader: &R, buf: &mut [u8]) {
+    std::ptr::write_bytes(buf.as_mut_ptr(), 0, buf.len())
+}
+
 #[cfg(test)]
 mod tests {
     use crate::io;
diff --git a/src/io/read/read_to_end.rs b/src/io/read/read_to_end.rs
index 331f26f..d76ee8c 100644
--- a/src/io/read/read_to_end.rs
+++ b/src/io/read/read_to_end.rs
@@ -64,7 +64,7 @@ pub fn read_to_end_internal<R: Read + ?Sized>(
                 g.buf.reserve(32);
                 let capacity = g.buf.capacity();
                 g.buf.set_len(capacity);
-                rd.initializer().initialize(&mut g.buf[g.len..]);
+                super::initialize(&rd, &mut g.buf[g.len..]);
             }
         }