diff --git a/packages/javascript/package.json b/packages/javascript/package.json
index b0080d5..f7f27d1 100644
--- a/packages/javascript/package.json
+++ b/packages/javascript/package.json
@@ -43,11 +43,11 @@
     "@types/node": "^22.0.0",
     "@typescript-eslint/eslint-plugin": "^8.0.0",
     "@typescript-eslint/parser": "^8.0.0",
-    "@vitest/coverage-v8": "^3.2.7",
+    "@vitest/coverage-v8": "^5.0.3",
     "eslint": "^9.0.0",
     "tsup": "^8.0.0",
     "typescript": "^5.6.0",
-    "vitest": "^3.2.7"
+    "vitest": "^5.0.3"
   },
   "engines": {
     "node": ">=18.0.0"
diff --git a/packages/javascript/vitest.config.ts b/packages/javascript/vitest.config.ts
index 02a862e..16041af 100644
--- a/packages/javascript/vitest.config.ts
+++ b/packages/javascript/vitest.config.ts
@@ -21,6 +21,9 @@ export default defineConfig({
       provider: 'v8',
       reporter: ['text', 'lcov'],
       include: ['src/**/*.ts'],
+      // Generated wasm-bindgen output and type declarations: not code under test, and
+      // vitest ≥4's coverage cannot parse ambient declarations (`export const x: T;`).
+      exclude: ['src/wasm-core/**', 'src/**/*.d.ts'],
     },
   },
 });