diff --git a/Cargo.toml b/Cargo.toml
index e38f090..a242cac 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -3,7 +3,7 @@ name = "quanta"
 version = "0.12.3"
 authors = ["Toby Lawrence <toby@nuclearfurnace.com>"]
 edition = "2021"
-rust-version = "1.60"
+rust-version = "1.70"
 
 license = "MIT"
 
diff --git a/src/clocks/monotonic/mod.rs b/src/clocks/monotonic/mod.rs
index b746333..80cbf89 100644
--- a/src/clocks/monotonic/mod.rs
+++ b/src/clocks/monotonic/mod.rs
@@ -3,10 +3,15 @@ mod windows;
 #[cfg(target_os = "windows")]
 pub use self::windows::Monotonic;
 
-#[cfg(target_arch = "wasm32")]
-mod wasm;
-#[cfg(target_arch = "wasm32")]
-pub use self::wasm::Monotonic;
+#[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
+mod wasm_browser;
+#[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
+pub use self::wasm_browser::Monotonic;
+
+#[cfg(all(target_arch = "wasm32", target_os = "wasi"))]
+mod wasm_wasi;
+#[cfg(all(target_arch = "wasm32", target_os = "wasi"))]
+pub use self::wasm_wasi::Monotonic;
 
 #[cfg(not(any(target_os = "windows", target_arch = "wasm32")))]
 mod unix;
diff --git a/src/clocks/monotonic/wasm.rs b/src/clocks/monotonic/wasm.rs
deleted file mode 100644
index 39a742b..0000000
--- a/src/clocks/monotonic/wasm.rs
+++ /dev/null
@@ -1,27 +0,0 @@
-const WASM_WRONG_ENV: &str = "failed to find the global `window` object: the `wasm32-unknown-unknown` implementation only supports running in web browsers; wse `wasm32-wasi` to run elsewhere";
-const WASM_MISSING_WINDOW_PERF: &str = "failed to find `window.performance`";
-
-#[derive(Clone, Copy, Debug, Default)]
-pub struct Monotonic {
-    _default: (),
-}
-
-#[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
-impl Monotonic {
-    pub fn now(&self) -> u64 {
-        let now = web_sys::window()
-            .expect(WASM_WRONG_ENV)
-            .performance()
-            .expect(WASM_MISSING_WINDOW_PERF)
-            .now();
-        // `window.performance.now()` returns the time in milliseconds.
-        return f64::trunc(now * 1_000_000.0) as u64;
-    }
-}
-
-#[cfg(all(target_arch = "wasm32", target_os = "wasi"))]
-impl Monotonic {
-    pub fn now(&self) -> u64 {
-        unsafe { wasi::clock_time_get(wasi::CLOCKID_MONOTONIC, 1).expect("failed to get time") }
-    }
-}
diff --git a/src/clocks/monotonic/wasm_browser.rs b/src/clocks/monotonic/wasm_browser.rs
new file mode 100644
index 0000000..b3f94a9
--- /dev/null
+++ b/src/clocks/monotonic/wasm_browser.rs
@@ -0,0 +1,39 @@
+use std::cell::OnceCell;
+
+use web_sys::{
+    js_sys::Reflect,
+    wasm_bindgen::{JsCast, JsValue},
+    Performance,
+};
+
+const WASM_MISSING_GLOBAL_THIS_PERF: &str = "failed to find `globalThis.performance`";
+const WASM_UNABLE_TO_CAST_PERF: &str =
+    "Unable to cast `globalThis.performance` to Performance type";
+
+thread_local! {
+    static GLOBAL_PERFORMANCE_INSTANCE: OnceCell<Performance> = const { OnceCell::new() };
+}
+
+#[derive(Clone, Copy, Debug, Default)]
+pub struct Monotonic {
+    _default: (),
+}
+
+impl Monotonic {
+    pub fn now(&self) -> u64 {
+        let now = GLOBAL_PERFORMANCE_INSTANCE.with(|value| {
+            let performance_instance = value.get_or_init(|| {
+                Reflect::get(
+                    &web_sys::js_sys::global(),
+                    &JsValue::from_str("performance"),
+                )
+                .expect(WASM_MISSING_GLOBAL_THIS_PERF)
+                .dyn_into::<Performance>()
+                .expect(WASM_UNABLE_TO_CAST_PERF)
+            });
+            performance_instance.now()
+        });
+        // `performance.now()` returns the time in milliseconds.
+        f64::trunc(now * 1_000_000.0) as u64
+    }
+}
diff --git a/src/clocks/monotonic/wasm_wasi.rs b/src/clocks/monotonic/wasm_wasi.rs
new file mode 100644
index 0000000..f230f68
--- /dev/null
+++ b/src/clocks/monotonic/wasm_wasi.rs
@@ -0,0 +1,10 @@
+#[derive(Clone, Copy, Debug, Default)]
+pub struct Monotonic {
+    _default: (),
+}
+
+impl Monotonic {
+    pub fn now(&self) -> u64 {
+        unsafe { wasi::clock_time_get(wasi::CLOCKID_MONOTONIC, 1).expect("failed to get time") }
+    }
+}