diff --git a/CHANGELOG.md b/CHANGELOG.md
index 15f521d2..25ab6b40 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # Changelog
 
+## Unreleased
+New: custom actions from chat messages and message cards now pass their data to your `Gleap.registerCustomAction` callback as `data` (next to `name` and `shareToken`), with a Messenger that sends it. Callbacks that only read `name` keep working.
+
 ## 19.3.3
 Fixed: charts and other SVG graphics could be missing from screenshots. An empty `<style>` inside an `<svg>` was captured as a stylesheet link to `null`, and the screenshot then dropped everything in the svg after it. Inline style sheets now always stay `<style>` elements; linked style sheets whose rules can't be read are still linked.
 
diff --git a/index.d.ts b/index.d.ts
index d868c48f..71d91ef4 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -118,7 +118,13 @@ export namespace Gleap {
     ) => string | object | Promise<string | object>
   ): void;
   function registerCustomAction(
-    customAction: (action: { name: string }) => void
+    customAction: (action: {
+      name: string;
+      /** The action's data (a message button's actionData), when it has some. */
+      data?: any;
+      /** The share token of the conversation the action was clicked in. */
+      shareToken?: string;
+    }) => void
   ): void;
   function log(message: string, logLevel?: "INFO" | "WARNING" | "ERROR"): void;
   /**
diff --git a/src/GleapFrameManager.js b/src/GleapFrameManager.js
index e81ea4e4..cc7a0405 100644
--- a/src/GleapFrameManager.js
+++ b/src/GleapFrameManager.js
@@ -1205,6 +1205,11 @@ export default class GleapFrameManager {
       if (data.name === 'run-custom-action') {
         GleapCustomActionManager.triggerCustomAction(data.data, {
           shareToken: data.shareToken,
+          // The action's payload (data-action-data / a card button's
+          // actionData), sent by Messenger versions that have it.
+          ...(data.actionData !== undefined && data.actionData !== null
+            ? { data: data.actionData }
+            : {}),
         });
       }