diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index e301510b..bf4cd9c0 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -272,14 +272,18 @@ jobs:
         run: cargo build --target riscv32i-unknown-none-elf
 
   unsupported:
-    name: Runtime error
+    name: Wasm backend override (${{ matrix.backend }})
     runs-on: ubuntu-24.04
+    strategy:
+      matrix:
+        backend: [unsupported, custom]
+    env:
+      RUSTFLAGS: -Dwarnings --cfg getrandom_backend="${{ matrix.backend }}"
     steps:
       - uses: actions/checkout@v7
       - uses: dtolnay/rust-toolchain@stable
         with:
           targets: wasm32-unknown-unknown
       - uses: Swatinem/rust-cache@v2
-      - env:
-          RUSTFLAGS: -Dwarnings --cfg getrandom_backend="unsupported"
-        run: cargo build --target wasm32-unknown-unknown
+      - run: cargo build --target wasm32-unknown-unknown
+      - run: cargo build --target wasm32-unknown-unknown --features wasm_js
diff --git a/src/error.rs b/src/error.rs
index 73a82743..03011da0 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -179,6 +179,11 @@ impl Error {
             Error::WINDOWS_RTL_GEN_RANDOM => "RtlGenRandom: Windows system function failure",
             #[cfg(all(
                 feature = "wasm_js",
+                not(any(
+                    getrandom_backend = "unsupported",
+                    getrandom_backend = "custom",
+                    getrandom_backend = "extern_impl",
+                )),
                 target_arch = "wasm32",
                 any(target_os = "unknown", target_os = "none")
             ))]