diff --git a/eslint.config.js b/eslint.config.js
index 03d96499..945fdb6a 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -115,6 +115,9 @@ export default tseslint.config(
 
             // Custom assertion functions
             'assertNetlifyToml',
+
+            // Vitest type testing functions
+            'expectTypeOf',
           ],
         },
       ],
diff --git a/packages/functions/src/global-types.test.ts b/packages/functions/src/global-types.test.ts
new file mode 100644
index 00000000..4ec42959
--- /dev/null
+++ b/packages/functions/src/global-types.test.ts
@@ -0,0 +1,13 @@
+import { describe, test, expectTypeOf } from 'vitest'
+import type { NetlifyGlobal } from '@netlify/types'
+
+// Import the main module to ensure global augmentation is loaded
+import './main.js'
+
+describe('Netlify global type declaration regression test', () => {
+  test('should augment global scope with `Netlify` global', () => {
+    expectTypeOf<typeof Netlify>().toEqualTypeOf<NetlifyGlobal>()
+    expectTypeOf<typeof Netlify>().toHaveProperty('env')
+    expectTypeOf<typeof Netlify>().toHaveProperty('context')
+  })
+})
diff --git a/packages/functions/src/main.ts b/packages/functions/src/main.ts
index a3154338..736ee659 100644
--- a/packages/functions/src/main.ts
+++ b/packages/functions/src/main.ts
@@ -1,3 +1,9 @@
+import type { NetlifyGlobal } from '@netlify/types'
+
+declare global {
+  const Netlify: NetlifyGlobal
+}
+
 export { builder } from './lib/builder.js'
 export { purgeCache } from './lib/purge_cache.js'
 export { schedule } from './lib/schedule.js'
diff --git a/packages/functions/tsconfig.json b/packages/functions/tsconfig.json
index 12ec691d..49490e9d 100644
--- a/packages/functions/tsconfig.json
+++ b/packages/functions/tsconfig.json
@@ -11,6 +11,7 @@
     "removeComments": false,
     "strict": true,
     "moduleResolution": "node",
+    "skipLibCheck": true,
     "forceConsistentCasingInFileNames": true
   },
   "include": ["src", "dev"]
diff --git a/packages/functions/vitest.config.ts b/packages/functions/vitest.config.ts
index 0bbc0597..6f0b1819 100644
--- a/packages/functions/vitest.config.ts
+++ b/packages/functions/vitest.config.ts
@@ -7,5 +7,8 @@ export default defineConfig({
   test: {
     include: ['(src|dev)/**/*.test.ts'],
     testTimeout: 30_000,
+    typecheck: {
+      enabled: true,
+    },
   },
 })
diff --git a/packages/types/src/main.test.ts b/packages/types/src/main.test.ts
index 1e77f5f6..72c2acd2 100644
--- a/packages/types/src/main.test.ts
+++ b/packages/types/src/main.test.ts
@@ -4,12 +4,12 @@ import { fileURLToPath } from 'node:url'
 
 import { expect, expectTypeOf, test } from 'vitest'
 
-import { Context, NetlifyGlobal } from './main.js'
+import type { Context, NetlifyGlobal } from './main.js'
 import * as main from './main.js'
 
 test('Exports types', () => {
-  expectTypeOf<Context>()
-  expectTypeOf<NetlifyGlobal>()
+  expectTypeOf<Context>().toExtend<object>()
+  expectTypeOf<NetlifyGlobal>().toExtend<object>()
 })
 
 test('Does not export runtime code', () => {
diff --git a/packages/types/vitest.config.ts b/packages/types/vitest.config.ts
new file mode 100644
index 00000000..4428598a
--- /dev/null
+++ b/packages/types/vitest.config.ts
@@ -0,0 +1,9 @@
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    typecheck: {
+      enabled: true,
+    },
+  },
+})