diff --git a/test/unit/property-effects.html b/test/unit/property-effects.html
index 3de0bfb660..d42d1704e5 100644
--- a/test/unit/property-effects.html
+++ b/test/unit/property-effects.html
@@ -1402,7 +1402,7 @@
 
 suite('runtime effects', function() {
 
-  var el;
+  var el, el2;
 
   setup(function() {
     el = document.createElement('x-basic');
@@ -1411,6 +1411,7 @@
 
   teardown(function() {
     document.body.removeChild(el);
+    document.body.removeChild(el2);
   });
 
   test('add/remove runtime property effect', function() {
@@ -1429,6 +1430,10 @@
     el._removePropertyEffect('value', el.PROPERTY_EFFECT_TYPES.OBSERVE, effect);
     el.value = 'value+++';
     assert.equal(fn.callCount, 1);
+    // Ensure prototype wasn't affected
+    el2 = document.createElement('x-basic');
+    document.body.appendChild(el2);
+    assert.equal(fn.callCount, 1);
   });
 
   test('add/remove runtime path effect', function() {
@@ -1455,6 +1460,10 @@
     el._removePropertyEffect('value', el.PROPERTY_EFFECT_TYPES.OBSERVE, effect);
     el.set('value.path', 'value.path+++');
     assert.equal(fn.callCount, 2);
+    // Ensure prototype wasn't affected
+    el2 = document.createElement('x-basic');
+    document.body.appendChild(el2);
+    assert.equal(fn.callCount, 2);
   });
 
 });