diff --git a/bindings/matrix-sdk-crypto-js/scripts/build.sh b/bindings/matrix-sdk-crypto-js/scripts/build.sh
index f782a2b2e..2c3caeb5f 100755
--- a/bindings/matrix-sdk-crypto-js/scripts/build.sh
+++ b/bindings/matrix-sdk-crypto-js/scripts/build.sh
@@ -19,7 +19,11 @@ cd $(dirname "$0")/..
 RUSTFLAGS='-C opt-level=z' WASM_BINDGEN_WEAKREF=1 wasm-pack build --target nodejs --scope matrix-org --out-dir pkg "${WASM_PACK_ARGS[@]}"
 
 # Convert the Wasm into a JS file that exports the base64'ed Wasm.
-echo "module.exports = \`$(base64 pkg/matrix_sdk_crypto_js_bg.wasm)\`;" > pkg/matrix_sdk_crypto_js_bg.wasm.js
+{
+  printf 'module.exports = `'
+  base64 < pkg/matrix_sdk_crypto_js_bg.wasm
+  printf '`;'
+} > pkg/matrix_sdk_crypto_js_bg.wasm.js
 
 # In the JavaScript:
 #  1. Strip out the lines that load the WASM, and our new epilogue.