diff --git a/index.ts b/index.ts
index 4eeb7d3..a4ffd45 100644
--- a/index.ts
+++ b/index.ts
@@ -317,7 +317,13 @@ function downloadNpmPackage(name: string, version: string, outDir: string): stri
     const fullName = `${npmName}@${version}`;
     const cpOpts = { encoding: "utf8", maxBuffer: 100 * 1024 * 1024 } as const;
     const npmPack = cp.execFileSync("npm", ["pack", fullName, "--json", "--silent"], cpOpts).trim();
-    const tarballName = npmPack.endsWith(".tgz") ? npmPack : JSON.parse(npmPack)[0].filename as string;
+    let tarballName = npmPack.endsWith(".tgz") ? npmPack : JSON.parse(npmPack)[0].filename as string;
+    
+    // Npm does not report the correct filename for scoped packages. See https://github.com/npm/cli/issues/3405.
+    if (!fs.existsSync(tarballName)) {
+        tarballName = tarballName.replace(/^@/, '').replace(/\//, '-');
+    }
+
     const outPath = path.join(outDir, name);
     initDir(outPath);
     const args = os.platform() === "darwin"