diff --git a/themes/bubble.ts b/themes/bubble.ts
index 0bccb14b99..58f853d848 100644
--- a/themes/bubble.ts
+++ b/themes/bubble.ts
@@ -92,6 +92,8 @@ class BubbleTooltip extends BaseTooltip {
 }
 
 class BubbleTheme extends BaseTheme {
+  public tooltip: BubbleTooltip;
+
   constructor(quill, options) {
     if (
       options.modules.toolbar != null &&