diff --git a/extensions/msteams/src/messenger.ts b/extensions/msteams/src/messenger.ts
index ff6f1e58485..1ee0cae68e4 100644
--- a/extensions/msteams/src/messenger.ts
+++ b/extensions/msteams/src/messenger.ts
@@ -295,7 +295,7 @@ async function buildActivity(
       // Teams only accepts base64 data URLs for images
       const conversationType = conversationRef.conversation?.conversationType?.toLowerCase();
       const isPersonal = conversationType === "personal";
-      const isImage = contentType?.startsWith("image/") ?? false;
+      const isImage = media.kind === "image";
 
       if (
         requiresFileConsent({
@@ -347,7 +347,7 @@ async function buildActivity(
         return activity;
       }
 
-      if (!isPersonal && !isImage && tokenProvider) {
+      if (!isPersonal && media.kind !== "image" && tokenProvider) {
         // Fallback: no SharePoint site configured, try OneDrive upload
         const uploaded = await uploadAndShareOneDrive({
           buffer: media.buffer,