diff --git a/rust/hg-core/src/lock.rs b/rust/hg-core/src/lock.rs
--- a/rust/hg-core/src/lock.rs
+++ b/rust/hg-core/src/lock.rs
@@ -2,7 +2,6 @@
 
 use crate::errors::HgError;
 use crate::errors::HgResultExt;
-use crate::utils::StrExt;
 use crate::vfs::Vfs;
 use std::io;
 use std::io::ErrorKind;
@@ -107,7 +106,7 @@ fn unlock(hg_vfs: Vfs, lock_filename: &s
 /// running anymore.
 fn lock_should_be_broken(data: &Option<String>) -> bool {
     (|| -> Option<bool> {
-        let (prefix, pid) = data.as_ref()?.split_2(':')?;
+        let (prefix, pid) = data.as_ref()?.split_once(':')?;
         if prefix != &*LOCK_PREFIX {
             return Some(false);
         }
diff --git a/rust/hg-core/src/utils.rs b/rust/hg-core/src/utils.rs
--- a/rust/hg-core/src/utils.rs
+++ b/rust/hg-core/src/utils.rs
@@ -145,21 +145,6 @@ impl SliceExt for [u8] {
     }
 }
 
-pub trait StrExt {
-    // TODO: Use https://doc.rust-lang.org/nightly/std/primitive.str.html#method.split_once
-    // once we require Rust 1.52+
-    fn split_2(&self, separator: char) -> Option<(&str, &str)>;
-}
-
-impl StrExt for str {
-    fn split_2(&self, separator: char) -> Option<(&str, &str)> {
-        let mut iter = self.splitn(2, separator);
-        let a = iter.next()?;
-        let b = iter.next()?;
-        Some((a, b))
-    }
-}
-
 pub trait Escaped {
     /// Return bytes escaped for display to the user
     fn escaped_bytes(&self) -> Vec<u8>;