diff --git a/public/scripts/extensions/caption/index.js b/public/scripts/extensions/caption/index.js
index d981c15a6..d7a167fd4 100644
--- a/public/scripts/extensions/caption/index.js
+++ b/public/scripts/extensions/caption/index.js
@@ -1,4 +1,4 @@
-import { getBase64Async, isTrueBoolean, saveBase64AsFile } from '../../utils.js';
+import { ensureImageFormatSupported, getBase64Async, isTrueBoolean, saveBase64AsFile } from '../../utils.js';
 import { getContext, getApiUrl, doExtrasFetch, extension_settings, modules, renderExtensionTemplateAsync } from '../../extensions.js';
 import { callPopup, getRequestHeaders, saveSettingsDebounced, substituteParamsExtended } from '../../../script.js';
 import { getMessageTimeStamp } from '../../RossAscends-mods.js';
@@ -272,7 +272,7 @@ async function getCaptionForFile(file, prompt, quiet) {
     try {
         setSpinnerIcon();
         const context = getContext();
-        const fileData = await getBase64Async(file);
+        const fileData = await getBase64Async(await ensureImageFormatSupported(file));
         const base64Format = fileData.split(',')[0].split(';')[0].split('/')[1];
         const base64Data = fileData.split(',')[1];
         const { caption } = await doCaptionRequest(base64Data, fileData, prompt);