diff --git a/Cargo.lock b/Cargo.lock
index 5b3195d..b229d58 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -127,7 +127,7 @@ dependencies = [
  "dunce",
  "escargot",
  "libtest2-harness",
- "once_cell",
+ "once_cell_polyfill",
  "pathdiff",
  "snapbox",
 ]
@@ -153,7 +153,7 @@ dependencies = [
  "dunce",
  "escargot",
  "libtest2-harness",
- "once_cell",
+ "once_cell_polyfill",
  "pathdiff",
  "snapbox",
 ]
@@ -179,6 +179,15 @@ version = "1.19.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3fdb12b2476b595f9358c5161aa467c2438859caa136dec86c26fdd2efe17b92"
 
+[[package]]
+name = "once_cell_polyfill"
+version = "1.70.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2611b99ab098a31bdc8be48b4f1a285ca0ced28bd5b4f23e45efa8c63b09efa5"
+dependencies = [
+ "once_cell",
+]
+
 [[package]]
 name = "pathdiff"
 version = "0.2.1"
diff --git a/crates/libtest2-mimic/Cargo.toml b/crates/libtest2-mimic/Cargo.toml
index 632c31d..15886a5 100644
--- a/crates/libtest2-mimic/Cargo.toml
+++ b/crates/libtest2-mimic/Cargo.toml
@@ -36,7 +36,7 @@ libtest2-harness = { version = "0.1.0", path = "../libtest2-harness" }
 cmd = "0.0.0"
 dunce = "1.0.4"
 escargot = "0.5.8"
-once_cell = "1.19.0"
+once_cell_polyfill = "1.56.0"
 pathdiff = "0.2.1"
 snapbox = "0.5.0"
 
diff --git a/crates/libtest2-mimic/tests/testsuite/all_passing.rs b/crates/libtest2-mimic/tests/testsuite/all_passing.rs
index b36d00c..3d363f5 100644
--- a/crates/libtest2-mimic/tests/testsuite/all_passing.rs
+++ b/crates/libtest2-mimic/tests/testsuite/all_passing.rs
@@ -1,6 +1,6 @@
 fn test_cmd() -> snapbox::cmd::Command {
-    static BIN: once_cell::sync::OnceCell<(std::path::PathBuf, std::path::PathBuf)> =
-        once_cell::sync::OnceCell::new();
+    static BIN: once_cell_polyfill::sync::OnceLock<(std::path::PathBuf, std::path::PathBuf)> =
+        once_cell_polyfill::sync::OnceLock::new();
     let (bin, current_dir) = BIN.get_or_init(|| {
         let package_root = crate::util::new_test(
             r#"
diff --git a/crates/libtest2-mimic/tests/testsuite/mixed_bag.rs b/crates/libtest2-mimic/tests/testsuite/mixed_bag.rs
index 56eb28a..4f1c949 100644
--- a/crates/libtest2-mimic/tests/testsuite/mixed_bag.rs
+++ b/crates/libtest2-mimic/tests/testsuite/mixed_bag.rs
@@ -1,6 +1,6 @@
 fn test_cmd() -> snapbox::cmd::Command {
-    static BIN: once_cell::sync::OnceCell<(std::path::PathBuf, std::path::PathBuf)> =
-        once_cell::sync::OnceCell::new();
+    static BIN: once_cell_polyfill::sync::OnceLock<(std::path::PathBuf, std::path::PathBuf)> =
+        once_cell_polyfill::sync::OnceLock::new();
     let (bin, current_dir) = BIN.get_or_init(|| {
         let package_root = crate::util::new_test(
             r#"
diff --git a/crates/libtest2-mimic/tests/testsuite/panic.rs b/crates/libtest2-mimic/tests/testsuite/panic.rs
index 6ccd5f4..f1a3413 100644
--- a/crates/libtest2-mimic/tests/testsuite/panic.rs
+++ b/crates/libtest2-mimic/tests/testsuite/panic.rs
@@ -1,6 +1,6 @@
 fn test_cmd() -> snapbox::cmd::Command {
-    static BIN: once_cell::sync::OnceCell<(std::path::PathBuf, std::path::PathBuf)> =
-        once_cell::sync::OnceCell::new();
+    static BIN: once_cell_polyfill::sync::OnceLock<(std::path::PathBuf, std::path::PathBuf)> =
+        once_cell_polyfill::sync::OnceLock::new();
     let (bin, current_dir) = BIN.get_or_init(|| {
         let package_root = crate::util::new_test(
             r#"
diff --git a/crates/libtest2/Cargo.toml b/crates/libtest2/Cargo.toml
index 8f5644f..e1ac732 100644
--- a/crates/libtest2/Cargo.toml
+++ b/crates/libtest2/Cargo.toml
@@ -36,7 +36,7 @@ libtest2-harness = { version = "0.1.0", path = "../libtest2-harness" }
 cmd = "0.0.0"
 dunce = "1.0.4"
 escargot = "0.5.8"
-once_cell = "1.19.0"
+once_cell_polyfill = "1.56.0"
 pathdiff = "0.2.1"
 snapbox = "0.5.0"
 
diff --git a/crates/libtest2/tests/testsuite/all_passing.rs b/crates/libtest2/tests/testsuite/all_passing.rs
index e68047d..657881f 100644
--- a/crates/libtest2/tests/testsuite/all_passing.rs
+++ b/crates/libtest2/tests/testsuite/all_passing.rs
@@ -1,6 +1,6 @@
 fn test_cmd() -> snapbox::cmd::Command {
-    static BIN: once_cell::sync::OnceCell<(std::path::PathBuf, std::path::PathBuf)> =
-        once_cell::sync::OnceCell::new();
+    static BIN: once_cell_polyfill::sync::OnceLock<(std::path::PathBuf, std::path::PathBuf)> =
+        once_cell_polyfill::sync::OnceLock::new();
     let (bin, current_dir) = BIN.get_or_init(|| {
         let package_root = crate::util::new_test(
             r#"
diff --git a/crates/libtest2/tests/testsuite/mixed_bag.rs b/crates/libtest2/tests/testsuite/mixed_bag.rs
index 897fcdc..9e354b4 100644
--- a/crates/libtest2/tests/testsuite/mixed_bag.rs
+++ b/crates/libtest2/tests/testsuite/mixed_bag.rs
@@ -1,6 +1,6 @@
 fn test_cmd() -> snapbox::cmd::Command {
-    static BIN: once_cell::sync::OnceCell<(std::path::PathBuf, std::path::PathBuf)> =
-        once_cell::sync::OnceCell::new();
+    static BIN: once_cell_polyfill::sync::OnceLock<(std::path::PathBuf, std::path::PathBuf)> =
+        once_cell_polyfill::sync::OnceLock::new();
     let (bin, current_dir) = BIN.get_or_init(|| {
         let package_root = crate::util::new_test(
             r#"
diff --git a/crates/libtest2/tests/testsuite/panic.rs b/crates/libtest2/tests/testsuite/panic.rs
index b7a587f..f672a7f 100644
--- a/crates/libtest2/tests/testsuite/panic.rs
+++ b/crates/libtest2/tests/testsuite/panic.rs
@@ -1,6 +1,6 @@
 fn test_cmd() -> snapbox::cmd::Command {
-    static BIN: once_cell::sync::OnceCell<(std::path::PathBuf, std::path::PathBuf)> =
-        once_cell::sync::OnceCell::new();
+    static BIN: once_cell_polyfill::sync::OnceLock<(std::path::PathBuf, std::path::PathBuf)> =
+        once_cell_polyfill::sync::OnceLock::new();
     let (bin, current_dir) = BIN.get_or_init(|| {
         let package_root = crate::util::new_test(
             r#"