diff --git a/Makefile b/Makefile
index 22533c0f4..7c6b6f3eb 100644
--- a/Makefile
+++ b/Makefile
@@ -89,6 +89,9 @@ dist/pyodide.d.ts: src/js/*.ts src/js/pyproxy.gen.ts src/js/error_handling.gen.t
 src/js/error_handling.gen.ts : src/core/error_handling.ts
 	cp $< $@
 
+%.wasm.gen.js: %.wat
+	node tools/assemble_wat.js $@
+
 src/js/pyproxy.gen.ts : src/core/pyproxy.* src/core/*.h
 	# We can't input pyproxy.js directly because CC will be unhappy about the file
 	# extension. Instead cat it and have CC read from stdin.
diff --git a/tools/assemble_wat.js b/tools/assemble_wat.js
new file mode 100644
index 000000000..eb8a710ca
--- /dev/null
+++ b/tools/assemble_wat.js
@@ -0,0 +1,29 @@
+const fs = require("fs");
+const { execFileSync } = require("child_process");
+
+process.argv[2].split();
+
+const path = process.argv[2].split("/");
+const filename = path.pop().split(".")[0];
+process.chdir(path.join("/"));
+
+try {
+    execFileSync("wat2wasms", [filename + ".wat", "--enable-all"]);
+} catch (e) {
+    if (e.code === "ENOENT") {
+        process.stderr.write(
+            "assemble_wat.js: wat2wasm is not on path. " +
+                "Please install the WebAssembly Binary Toolkit.\n",
+        );
+        process.stderr.write("Quitting.\n");
+        process.exit(1);
+    }
+    throw e;
+}
+
+const f = fs.readFileSync(filename + ".wasm");
+fs.unlinkSync(filename + ".wasm");
+
+const s = Array.from(f, (x) => x.toString(16).padStart(2, "0")).join("");
+const output = `const ${filename}_wasm = decodeHexString("${s}");`;
+fs.writeFileSync(filename + ".wasm.gen.js", output);