diff --git a/CHANGELOG.md b/CHANGELOG.md
index bf489b2..152a72d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,10 @@
 
 -
 
+## 1.17.2
+
+- Avoid unnecessary synchronization in `Lazy::{force,deref}_mut()`, [#231](https://github.com/matklad/once_cell/pull/231).
+
 ## 1.17.1
 
 - Make `OnceRef` implementation compliant with [strict provenance](https://github.com/rust-lang/rust/issues/95228).
diff --git a/Cargo.lock.msrv b/Cargo.lock.msrv
index 6825f80..9edd508 100644
--- a/Cargo.lock.msrv
+++ b/Cargo.lock.msrv
@@ -45,7 +45,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "51887d4adc7b564537b15adcfb307936f8075dfcd5f00dde9a9f1d29383682bc"
 dependencies = [
  "cfg-if",
- "once_cell 1.14.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "once_cell 1.14.0",
 ]
 
 [[package]]
@@ -69,20 +69,21 @@ checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
 [[package]]
 name = "once_cell"
 version = "1.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f7254b99e31cad77da24b08ebf628882739a608578bb1bcdfc1f9c21260d7c0"
+
+[[package]]
+name = "once_cell"
+version = "1.17.2"
 dependencies = [
  "atomic-polyfill",
+ "critical-section",
  "crossbeam-utils",
  "lazy_static",
  "parking_lot_core",
  "regex",
 ]
 
-[[package]]
-name = "once_cell"
-version = "1.14.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2f7254b99e31cad77da24b08ebf628882739a608578bb1bcdfc1f9c21260d7c0"
-
 [[package]]
 name = "parking_lot_core"
 version = "0.9.3"
diff --git a/Cargo.toml b/Cargo.toml
index ad02c34..46f9c32 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "once_cell"
-version = "1.17.1"
+version = "1.17.2"
 authors = ["Aleksey Kladov <aleksey.kladov@gmail.com>"]
 license = "MIT OR Apache-2.0"
 edition = "2021"
diff --git a/src/lib.rs b/src/lib.rs
index 9239296..4c2d0e4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -796,8 +796,14 @@ pub mod unsync {
         /// assert_eq!(*lazy, 92);
         /// ```
         pub fn force_mut(this: &mut Lazy<T, F>) -> &mut T {
-            Self::force(this);
-            Self::get_mut(this).unwrap_or_else(|| unreachable!())
+            if this.cell.get_mut().is_none() {
+                let value = match this.init.get_mut().take() {
+                    Some(f) => f(),
+                    None => panic!("Lazy instance has previously been poisoned"),
+                };
+                this.cell = OnceCell::with_value(value);
+            }
+            this.cell.get_mut().unwrap_or_else(|| unreachable!())
         }
 
         /// Gets the reference to the result of this lazy value if
@@ -844,8 +850,7 @@ pub mod unsync {
 
     impl<T, F: FnOnce() -> T> DerefMut for Lazy<T, F> {
         fn deref_mut(&mut self) -> &mut T {
-            Lazy::force(self);
-            self.cell.get_mut().unwrap_or_else(|| unreachable!())
+            Lazy::force_mut(self)
         }
     }
 
@@ -1324,8 +1329,14 @@ pub mod sync {
         /// assert_eq!(Lazy::force_mut(&mut lazy), &mut 92);
         /// ```
         pub fn force_mut(this: &mut Lazy<T, F>) -> &mut T {
-            Self::force(this);
-            Self::get_mut(this).unwrap_or_else(|| unreachable!())
+            if this.cell.get_mut().is_none() {
+                let value = match this.init.get_mut().take() {
+                    Some(f) => f(),
+                    None => panic!("Lazy instance has previously been poisoned"),
+                };
+                this.cell = OnceCell::with_value(value);
+            }
+            this.cell.get_mut().unwrap_or_else(|| unreachable!())
         }
 
         /// Gets the reference to the result of this lazy value if
@@ -1372,8 +1383,7 @@ pub mod sync {
 
     impl<T, F: FnOnce() -> T> DerefMut for Lazy<T, F> {
         fn deref_mut(&mut self) -> &mut T {
-            Lazy::force(self);
-            self.cell.get_mut().unwrap_or_else(|| unreachable!())
+            Lazy::force_mut(self)
         }
     }
 
diff --git a/xtask/src/main.rs b/xtask/src/main.rs
index 9a26f0d..c4ac864 100644
--- a/xtask/src/main.rs
+++ b/xtask/src/main.rs
@@ -48,7 +48,21 @@ fn main() -> xshell::Result<()> {
         let _s = section("TEST_MSRV");
         let _e = push_toolchain(&sh, MSRV)?;
         sh.copy_file("Cargo.lock.msrv", "Cargo.lock")?;
-        cmd!(sh, "cargo build").run()?;
+        if let err @ Err(_) = cmd!(sh, "cargo update -w -v --locked").run() {
+            // `Cargo.lock.msrv` is out of date! Probably from having bumped our own version number.
+            println! {"\
+                Error: `Cargo.lock.msrv` is out of date. \
+                Please run:\n    \
+                (cp Cargo.lock{{.msrv,}} && cargo +{MSRV} update -w -v && cp Cargo.lock{{.msrv,}})\n\
+                \n\
+                Alternatively, `git apply` the `.patch` below:\
+            "}
+            cmd!(sh, "cargo update -q -w").quiet().run()?;
+            sh.copy_file("Cargo.lock", "Cargo.lock.msrv")?;
+            cmd!(sh, "git --no-pager diff --color=always -- Cargo.lock.msrv").quiet().run()?;
+            return err;
+        }
+        cmd!(sh, "cargo build --locked").run()?;
     }
 
     {