diff --git a/addon/-private/properties/collection.js b/addon/-private/properties/collection.js
index df7d9da6..a07a0447 100644
--- a/addon/-private/properties/collection.js
+++ b/addon/-private/properties/collection.js
@@ -1,4 +1,5 @@
 import { deprecate } from '@ember/application/deprecations';
+import { warn } from '@ember/debug';
 
 import { collection as mainCollection } from './collection/main';
 import { collection as legacyCollection } from './collection/legacy';
@@ -123,5 +124,13 @@ export function collection(scopeOrDefinition, definitionOrNothing) {
     url: 'https://gist.github.com/san650/17174e4b7b1fd80b049a47eb456a7cdc#file-old-collection-api-js',
   });
 
+  warn(
+    'Legacy page object collection definition is invalid. Please, make sure you include a `itemScope` selector.',
+    scopeOrDefinition.itemScope,
+    {
+      id: 'ember-cli-page-object.legacy-collection-missing-item-scope'
+    }
+  );
+
   return legacyCollection(scopeOrDefinition);
 }
diff --git a/tests/integration/deprecations/legacy-collection-test.js b/tests/integration/deprecations/legacy-collection-test.js
index 6bf718a5..c9709d8f 100644
--- a/tests/integration/deprecations/legacy-collection-test.js
+++ b/tests/integration/deprecations/legacy-collection-test.js
@@ -27,3 +27,12 @@ test("doesn't show a deprecation warning when first parameter is a string", func
 
   assert.expectNoDeprecation();
 });
+
+test('shows a warning on invalid legacy collection definitions', function(assert) {
+  assert.expectWarning(function() {
+    create({
+      foo: collection({
+      })
+    });
+  }, 'Legacy page object collection definition is invalid. Please, make sure you include a `itemScope` selector.');
+});