diff --git a/galaxy.js b/galaxy.js
index 21d92e2..3aac816 100644
--- a/galaxy.js
+++ b/galaxy.js
@@ -164,7 +164,7 @@ export function initGalaxy({
                     if (slot in saveCallbacks) {
                         return Promise.reject(`save action for slot ${slot} already in progress.`);
                     }
-                    galaxy.postMessage({ action: "save", slot, content, label });
+                    galaxy.postMessage({ action: "save", slot, data: content, label });
                     return new Promise((accept, reject) => {
                         saveCallbacks[slot] = { accept, reject };
                     });