diff --git a/demos/src/GuideContent/ExportHTML/React/index.jsx b/demos/src/GuideContent/ExportHTML/React/index.jsx
index ed6f333d..30dc671c 100644
--- a/demos/src/GuideContent/ExportHTML/React/index.jsx
+++ b/demos/src/GuideContent/ExportHTML/React/index.jsx
@@ -16,7 +16,7 @@ export default () => {
 
   useEffect(() => {
     if (!editor) {
-      return null
+      return undefined
     }
 
     // Get the initial content …
diff --git a/demos/src/GuideContent/ExportJSON/React/index.jsx b/demos/src/GuideContent/ExportJSON/React/index.jsx
index b452258f..c8888b39 100644
--- a/demos/src/GuideContent/ExportJSON/React/index.jsx
+++ b/demos/src/GuideContent/ExportJSON/React/index.jsx
@@ -16,7 +16,7 @@ export default () => {
 
   useEffect(() => {
     if (!editor) {
-      return null
+      return undefined
     }
 
     // Get the initial content …
diff --git a/demos/src/GuideContent/ReadOnly/React/index.jsx b/demos/src/GuideContent/ReadOnly/React/index.jsx
index 3d2dccfc..b5417585 100644
--- a/demos/src/GuideContent/ReadOnly/React/index.jsx
+++ b/demos/src/GuideContent/ReadOnly/React/index.jsx
@@ -20,7 +20,7 @@ export default () => {
 
   useEffect(() => {
     if (!editor) {
-      return null
+      return undefined
     }
 
     editor.setEditable(editable)