diff --git a/Cargo.toml b/Cargo.toml
index d50339be..c875d894 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,7 +22,7 @@ encoding_rs = "0.8"
 [dependencies]
 cssparser-macros = {path = "./macros", version = "0.6"}
 dtoa-short = "0.3"
-itoa = "0.4"
+itoa = "1.0"
 matches = "0.1"
 phf = {version = "0.8", features = ["macros"]}
 serde = {version = "1.0", optional = true}
diff --git a/src/serializer.rs b/src/serializer.rs
index abd50c3d..91fff839 100644
--- a/src/serializer.rs
+++ b/src/serializer.rs
@@ -6,7 +6,6 @@ use dtoa_short::{self, Notation};
 use itoa;
 use matches::matches;
 use std::fmt::{self, Write};
-use std::io;
 use std::str;
 
 use super::Token;
@@ -340,34 +339,9 @@ macro_rules! impl_tocss_for_int {
             where
                 W: fmt::Write,
             {
-                struct AssumeUtf8<W: fmt::Write>(W);
-
-                impl<W: fmt::Write> io::Write for AssumeUtf8<W> {
-                    #[inline]
-                    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
-                        // Safety: itoa only emits ASCII, which is also well-formed UTF-8.
-                        debug_assert!(buf.is_ascii());
-                        self.0
-                            .write_str(unsafe { str::from_utf8_unchecked(buf) })
-                            .map_err(|_| io::ErrorKind::Other.into())
-                    }
-
-                    #[inline]
-                    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-                        self.write_all(buf)?;
-                        Ok(buf.len())
-                    }
-
-                    #[inline]
-                    fn flush(&mut self) -> io::Result<()> {
-                        Ok(())
-                    }
-                }
-
-                match itoa::write(AssumeUtf8(dest), *self) {
-                    Ok(_) => Ok(()),
-                    Err(_) => Err(fmt::Error),
-                }
+                let mut buf = itoa::Buffer::new();
+                let s = buf.format(*self);
+                dest.write_str(s)
             }
         }
     };