diff --git a/packages/core/src/pattern.mjs b/packages/core/src/pattern.mjs
index 13b520c6baa..b782362fd78 100644
--- a/packages/core/src/pattern.mjs
+++ b/packages/core/src/pattern.mjs
@@ -122,7 +122,7 @@ Pattern.prototype.draft = function () {
 
 Pattern.prototype.createPartForSet = function (partName, set = 0) {
   // gotta protect against attacks
-  if (typeof set === '__proto__') {
+  if (set === '__proto__') {
     throw new Error('malicious attempt at altering Object.prototype. Stopping action')
   }
   // Create parts
diff --git a/packages/core/tests/pattern-draft.test.mjs b/packages/core/tests/pattern-draft.test.mjs
index d66459d6780..009f9581dfa 100644
--- a/packages/core/tests/pattern-draft.test.mjs
+++ b/packages/core/tests/pattern-draft.test.mjs
@@ -33,6 +33,18 @@ describe('Pattern', () => {
       expect(count).to.equal(2)
     })
   })
+  describe('Pattern.createPartForSet()', () => {
+    it('Should not allow malicious assignment to Object.prototype', () => {
+      const objProto = Object.prototype
+      const Pattern = new Design()
+      const pattern = new Pattern()
+
+      expect(() => pattern.createPartForSet('part', '__proto__')).to.throw(
+        'malicious attempt at altering Object.prototype. Stopping action'
+      )
+      expect(objProto).to.equal(Object.prototype)
+    })
+  })
   it('Should check whether a part is needed', () => {
     const partA = {
       name: 'test.partA',