diff --git a/src/compiler/output-targets/dist-hydrate-script/hydrate-factory-closure.ts b/src/compiler/output-targets/dist-hydrate-script/hydrate-factory-closure.ts
index 467765395fe..c844358ed7e 100644
--- a/src/compiler/output-targets/dist-hydrate-script/hydrate-factory-closure.ts
+++ b/src/compiler/output-targets/dist-hydrate-script/hydrate-factory-closure.ts
@@ -63,6 +63,7 @@ export function hydrateFactory($stencilWindow, $stencilHydrateOpts, $stencilHydr
   var HTMLTemplateElement = $stencilWindow.HTMLTemplateElement;
   var HTMLTitleElement = $stencilWindow.HTMLTitleElement;
   var IntersectionObserver = $stencilWindow.IntersectionObserver;
+  var ResizeObserver = $stencilWindow.ResizeObserver;
   var KeyboardEvent = $stencilWindow.KeyboardEvent;
   var MouseEvent = $stencilWindow.MouseEvent;
   var Node = $stencilWindow.Node;
diff --git a/src/mock-doc/resize-observer.ts b/src/mock-doc/resize-observer.ts
new file mode 100644
index 00000000000..2fdadd7f16a
--- /dev/null
+++ b/src/mock-doc/resize-observer.ts
@@ -0,0 +1,21 @@
+export class MockResizeObserver {
+  constructor() {
+    /**/
+  }
+
+  disconnect() {
+    /**/
+  }
+
+  observe() {
+    /**/
+  }
+
+  takeRecords(): any[] {
+    return [];
+  }
+
+  unobserve() {
+    /**/
+  }
+}
diff --git a/src/mock-doc/window.ts b/src/mock-doc/window.ts
index 6dded0f0f2b..3c0bc5e408b 100644
--- a/src/mock-doc/window.ts
+++ b/src/mock-doc/window.ts
@@ -21,6 +21,7 @@ import { MockLocation } from './location';
 import { MockNavigator } from './navigator';
 import { MockElement, MockHTMLElement, MockNode, MockNodeList } from './node';
 import { MockPerformance, resetPerformance } from './performance';
+import { MockResizeObserver } from './resize-observer';
 import { MockStorage } from './storage';
 
 const nativeClearInterval = clearInterval;
@@ -311,6 +312,10 @@ export class MockWindow {
     return MockIntersectionObserver;
   }
 
+  get ResizeObserver() {
+    return MockResizeObserver;
+  }
+
   get localStorage() {
     if (this.__localStorage == null) {
       this.__localStorage = new MockStorage();