diff --git a/package-lock.json b/package-lock.json
index 0ae4183..e1cf0e7 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -10,7 +10,8 @@
             "license": "BSD-3-Clause",
             "dependencies": {
                 "@jupyterlite/contents": "^0.4.1",
-                "comlink": "^4.4.1"
+                "comlink": "^4.4.1",
+                "zod": "^3.23.8"
             },
             "devDependencies": {
                 "@rspack/cli": "^1.0.3",
@@ -1552,6 +1553,7 @@
             "version": "8.17.1",
             "resolved": "https://registry.npmjs.org/ajv/-/ajv-8.17.1.tgz",
             "integrity": "sha512-B/gBuNg5SiMTrPkC+A2+cW0RszwxYmn6VYxB/inlBStS5nx6xHIt/ehKRhIMhqusl7a8LjQoZnjCs5vhwxOQ1g==",
+            "license": "MIT",
             "dependencies": {
                 "fast-deep-equal": "^3.1.3",
                 "fast-uri": "^3.0.1",
@@ -6338,6 +6340,15 @@
             "funding": {
                 "url": "https://github.com/sponsors/sindresorhus"
             }
+        },
+        "node_modules/zod": {
+            "version": "3.23.8",
+            "resolved": "https://registry.npmjs.org/zod/-/zod-3.23.8.tgz",
+            "integrity": "sha512-XBx9AXhXktjUqnepgTiE5flcKIYWi/rme0Eaj+5Y0lftuGBq+jyRu/md4WnuxqgP1ubdpNCsYEYPxrzVHD8d6g==",
+            "license": "MIT",
+            "funding": {
+                "url": "https://github.com/sponsors/colinhacks"
+            }
         }
     }
 }
diff --git a/package.json b/package.json
index 245daf5..2060d53 100644
--- a/package.json
+++ b/package.json
@@ -33,7 +33,8 @@
     },
     "dependencies": {
         "@jupyterlite/contents": "^0.4.1",
-        "comlink": "^4.4.1"
+        "comlink": "^4.4.1",
+        "zod": "^3.23.8"
     },
     "devDependencies": {
         "@rspack/cli": "^1.0.3",
diff --git a/src/tools/prepare_wasm.ts b/src/tools/prepare_wasm.ts
index ae39509..86f26fb 100644
--- a/src/tools/prepare_wasm.ts
+++ b/src/tools/prepare_wasm.ts
@@ -11,6 +11,7 @@
 const fs = require('node:fs');
 const path = require('node:path');
 const { execSync } = require('node:child_process');
+const zod = require('zod');
 /* eslint-enable */
 
 const ENV_NAME = 'cockle_wasm_env';
@@ -39,6 +40,26 @@ if (fs.existsSync(otherConfigFilename)) {
   cockleConfig = cockleConfig.concat(extraConfig);
 }
 
+// Validate input schema, raising ZodError if fails.
+const inputSchema = zod.array(
+  zod
+    .object({
+      package: zod.string(),
+      modules: zod.optional(
+        zod.array(
+          zod
+            .object({
+              name: zod.string(),
+              commands: zod.optional(zod.string())
+            })
+            .strict()
+        )
+      )
+    })
+    .strict()
+);
+inputSchema.parse(cockleConfig);
+
 // Required emscripten-wasm32 packages.
 const packageNames = cockleConfig.map((item: any) => item.package);
 console.log('Required package names', packageNames);
@@ -87,6 +108,28 @@ for (const packageConfig of cockleConfig) {
   }
 }
 
+// Validate output schema, raising ZodError if fails.
+const outputSchema = zod.array(
+  zod
+    .object({
+      package: zod.string(),
+      build_string: zod.string(),
+      platform: zod.string(),
+      version: zod.string(),
+      channel: zod.string(),
+      modules: zod.array(
+        zod
+          .object({
+            name: zod.string(),
+            commands: zod.string()
+          })
+          .strict()
+      )
+    })
+    .strict()
+);
+outputSchema.parse(cockleConfig);
+
 // Output config file.
 let targetConfigFile = 'cockle-config.json';
 if (wantCopy) {