diff --git a/babel-plugin-joke/src/index.test.ts b/babel-plugin-joke/src/index.test.ts
index 208043f..142ad51 100644
--- a/babel-plugin-joke/src/index.test.ts
+++ b/babel-plugin-joke/src/index.test.ts
@@ -79,19 +79,16 @@ bar.mockReturnValue(5);"
 `);
 });
 
-it("ignores mock calls inside closures", async () => {
-  const result = await assert(`
+it("throws error if mock is called inside closures", async () => {
+  const result = assert(`
     import { mock } from '@userlike/joke';
     beforeEach(() => {
       const { foo } = mock(import('foo'));
     });
     `);
-  expect(result).toMatchInlineSnapshot(`
-"import { foo as _foo } from \\"foo\\";
-import { mock } from '@userlike/joke';
-jest.mock(\\"foo\\");
-beforeEach(() => {});"
-`);
+  expect(result).rejects.toMatchInlineSnapshot(
+    `[Error: /example.ts: Can only use \`mock\` at the top-level scope.]`
+  );
 });
 
 it("throws a sensible error", async () => {
diff --git a/babel-plugin-joke/src/index.ts b/babel-plugin-joke/src/index.ts
index 752e081..bf27722 100644
--- a/babel-plugin-joke/src/index.ts
+++ b/babel-plugin-joke/src/index.ts
@@ -53,7 +53,14 @@ export default function UserlikeJoke({
           })
           .map(path => path.parentPath);
 
-        const mockRefPaths = namedMockRefs.concat(namespaceMockRefs);
+        const mockRefPaths = namedMockRefs
+          .concat(namespaceMockRefs)
+          .filter(path => {
+            if (path.scope.getProgramParent() !== path.scope) {
+              throw new Error("Can only use `mock` at the top-level scope.");
+            }
+            return true;
+          });
 
         mockRefPaths.forEach(process(t, path));
       }