diff --git a/src/gui/src/IPC.js b/src/gui/src/IPC.js
index f76ccd20c..6d7e35866 100644
--- a/src/gui/src/IPC.js
+++ b/src/gui/src/IPC.js
@@ -1315,6 +1315,13 @@ const ipc_listener = async (event, handled) => {
             $(el_filedialog_window).close();
             window.show_save_account_notice_if_needed();
         };
+
+        const tell_caller_its_cancelled = async () => {
+            target_iframe.contentWindow.postMessage({
+                msg: "fileSaveCancelled", 
+                original_msg_id: msg_id, 
+            }, '*');
+        };
         
         const write_file_tell_caller_and_update_views = async ({
             target_path, el_filedialog_window,
@@ -1468,6 +1475,7 @@ const ipc_listener = async (event, handled) => {
             iframe_msg_uid: msg_id,
             center: true,
             initiating_app_uuid: app_uuid,
+            onDialogCancel: () => tell_caller_its_cancelled(),
             onSaveFileDialogSave: async function(target_path, el_filedialog_window){
                 $(el_filedialog_window).find('.window-disable-mask, .busy-indicator').show();
                 let busy_init_ts = Date.now();
diff --git a/src/gui/src/UI/UIWindow.js b/src/gui/src/UI/UIWindow.js
index e7627d033..3fa4f8349 100644
--- a/src/gui/src/UI/UIWindow.js
+++ b/src/gui/src/UI/UIWindow.js
@@ -896,6 +896,7 @@ async function UIWindow(options) {
                 $(`.window[data-element_uuid="${options.parent_uuid}"]`).find('.window-disable-mask').hide();
                 $(el_window).close();
             })
+            if ( options.onDialogCancel ) options.onDialogCancel.call(el_window);
         })
     }
 
diff --git a/src/puter-js/src/modules/UI.js b/src/puter-js/src/modules/UI.js
index 7192e7d8b..fb28d4498 100644
--- a/src/puter-js/src/modules/UI.js
+++ b/src/puter-js/src/modules/UI.js
@@ -1,6 +1,9 @@
 import FSItem from './FSItem.js';
 import PuterDialog from './PuterDialog.js';
 import EventListener  from '../lib/EventListener.js';
+import putility from '@heyputer/putility';
+
+const FILE_SAVE_CANCELLED = Symbol('FILE_SAVE_CANCELLED');
 
 // AppConnection provides an API for interacting with another app.
 // It's returned by UI methods, and cannot be constructed directly by user code.
@@ -467,6 +470,10 @@ class UI extends EventListener {
                     // execute callback
                     this.#callbackFunctions[e.data.original_msg_id](new FSItem(e.data.saved_file)); 
                 }
+                else if(e.data.msg === "fileSaveCancelled"){
+                    // execute callback
+                    this.#callbackFunctions[e.data.original_msg_id](FILE_SAVE_CANCELLED);
+                }
                 else{
                     // execute callback
                     this.#callbackFunctions[e.data.original_msg_id](e.data);
@@ -726,7 +733,8 @@ class UI extends EventListener {
     }
 
     showSaveFilePicker = function(content, suggestedName, type){
-        return new Promise((resolve, reject) => {
+        const undefinedOnCancel = new putility.libs.promise.TeePromise();
+        const resolveOnlyPromise = new Promise((resolve, reject) => {
             if (!globalThis.open) {
                 return reject("This API is not compatible in Web Workers.");
             }
@@ -782,8 +790,20 @@ class UI extends EventListener {
                 'toolbar=no, location=no, directories=no, status=no, menubar=no, scrollbars=no, resizable=no, copyhistory=no, width='+w+', height='+h+', top='+top+', left='+left);
             }
             //register callback
-            this.#callbackFunctions[msg_id] = resolve;
-        })
+            this.#callbackFunctions[msg_id] = (maybe_result) => {
+                // Only resolve cancel events if this was called with `.undefinedOnCancel`
+                if ( maybe_result === FILE_SAVE_CANCELLED ) {
+                    undefinedOnCancel.resolve(undefined);
+                    return;
+                }
+                undefinedOnCancel.resolve(maybe_result);
+                resolve(maybe_result);
+            };
+        });
+        
+        resolveOnlyPromise.undefinedOnCancel = undefinedOnCancel;
+        
+        return resolveOnlyPromise;
     }
 
     setWindowTitle = function(title, window_id, callback) {