diff --git a/.cargo/config b/.cargo/config
index be3061ab..b39926f8 100644
--- a/.cargo/config
+++ b/.cargo/config
@@ -1,6 +1,8 @@
 # Allow normal use of "cargo run" and "cargo test" on these wasm32 platforms.
 [target.wasm32-unknown-unknown]
 runner = 'wasm-bindgen-test-runner'
+[target.wasm64-unknown-unknown]
+runner = 'wasm-bindgen-test-runner'
 [target.wasm32-wasi]
 runner = 'wasmtime'
 
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 210d67ba..4ff11988 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -217,6 +217,21 @@ jobs:
       - name: Test (custom getrandom)
         run: cargo test --target=wasm32-unknown-unknown --features=custom
 
+  wasm64-tests:
+    name: WASM memory64
+    runs-on: ubuntu-latest
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly
+      - uses: Swatinem/rust-cache@v1
+      - name: Build and Link tests (build-std)
+        # This target is Tier 3, so we have to build libstd ourselves.
+        # We currently cannot run these tests because wasm-bindgen-test-runner
+        # does not yet support memory64.
+        run: cargo test --no-run -Z build-std=std,panic_abort --target=wasm64-unknown-unknown --features=js
+
   wasi-tests:
     name: WASI test
     runs-on: ubuntu-latest
diff --git a/Cargo.toml b/Cargo.toml
index 2024c8f9..90b36c6b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -23,10 +23,10 @@ libc = { version = "0.2.120", default-features = false }
 [target.'cfg(target_os = "wasi")'.dependencies]
 wasi = "0.11"
 
-[target.'cfg(all(target_arch = "wasm32", target_os = "unknown"))'.dependencies]
+[target.'cfg(all(any(target_arch = "wasm32", target_arch = "wasm64"), target_os = "unknown"))'.dependencies]
 wasm-bindgen = { version = "0.2.62", default-features = false, optional = true }
 js-sys = { version = "0.3", optional = true }
-[target.'cfg(all(target_arch = "wasm32", target_os = "unknown"))'.dev-dependencies]
+[target.'cfg(all(any(target_arch = "wasm32", target_arch = "wasm64"), target_os = "unknown"))'.dev-dependencies]
 wasm-bindgen-test = "0.3.18"
 
 [features]
@@ -34,7 +34,7 @@ wasm-bindgen-test = "0.3.18"
 std = []
 # Feature to enable fallback RDRAND-based implementation on x86/x86_64
 rdrand = []
-# Feature to enable JavaScript bindings on wasm32-unknown-unknown
+# Feature to enable JavaScript bindings on wasm*-unknown-unknown
 js = ["wasm-bindgen", "js-sys"]
 # Feature to enable custom RNG implementations
 custom = []
diff --git a/src/lib.rs b/src/lib.rs
index 074a6a7a..cd96fa5e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -30,7 +30,7 @@
 //! | ESP-IDF           | `*‑espidf`         | [`esp_fill_random`]
 //! | Emscripten        | `*‑emscripten`     | `/dev/random` (identical to `/dev/urandom`)
 //! | WASI              | `wasm32‑wasi`      | [`random_get`]
-//! | Web Browser and Node.js | `wasm32‑*‑unknown` | [`Crypto.getRandomValues`] if available, then [`crypto.randomFillSync`] if on Node.js, see [WebAssembly support]
+//! | Web Browser and Node.js | `wasm*‑*‑unknown` | [`Crypto.getRandomValues`] if available, then [`crypto.randomFillSync`] if on Node.js, see [WebAssembly support]
 //! | SOLID             | `*-kmc-solid_*`    | `SOLID_RNG_SampleRandomBytes`
 //! | Nintendo 3DS      | `armv6k-nintendo-3ds` | [`getrandom`][1]
 //!
@@ -256,9 +256,18 @@ cfg_if! {
     } else if #[cfg(all(feature = "rdrand",
                         any(target_arch = "x86_64", target_arch = "x86")))] {
         #[path = "rdrand.rs"] mod imp;
-    } else if #[cfg(all(feature = "js",
-                        target_arch = "wasm32", target_os = "unknown"))] {
-        #[path = "js.rs"] mod imp;
+    } else if #[cfg(all(any(target_arch = "wasm32", target_arch = "wasm64"),
+                        target_os = "unknown"))] {
+        cfg_if! {
+            if #[cfg(feature = "js")] {
+                #[path = "js.rs"] mod imp;
+            } else {
+                compile_error!("the wasm*-unknown-unknown targets are not \
+                                supported by default, you may need to enable \
+                                the \"js\" feature. For more information see: \
+                                https://docs.rs/getrandom/#webassembly-support");
+            }
+        }
     } else if #[cfg(all(target_os = "horizon", target_arch = "arm"))] {
         // We check for target_arch = "arm" because the Nintendo Switch also
         // uses Horizon OS (it is aarch64).
@@ -266,11 +275,6 @@ cfg_if! {
         #[path = "3ds.rs"] mod imp;
     } else if #[cfg(feature = "custom")] {
         use custom as imp;
-    } else if #[cfg(all(target_arch = "wasm32", target_os = "unknown"))] {
-        compile_error!("the wasm32-unknown-unknown target is not supported by \
-                        default, you may need to enable the \"js\" feature. \
-                        For more information see: \
-                        https://docs.rs/getrandom/#webassembly-support");
     } else {
         compile_error!("target is not supported, for more information see: \
                         https://docs.rs/getrandom/#unsupported-targets");