diff --git a/lib/shared/message-utils.js b/lib/shared/message-utils.js
--- a/lib/shared/message-utils.js
+++ b/lib/shared/message-utils.js
@@ -290,16 +290,24 @@
   });
 }
 
+function reactionMessagePreview(): string {
+  return 'reacted to a message';
+}
+
 function messagePreviewText(
   messageInfo: PreviewableMessageInfo,
   threadInfo: ThreadInfo,
 ): string {
   if (
     messageInfo.type === messageTypes.IMAGES ||
-    messageInfo.type === messageTypes.MULTIMEDIA
+    messageInfo.type === messageTypes.MULTIMEDIA ||
+    messageInfo.type === messageTypes.REACTION
   ) {
     const creator = stringForUser(messageInfo.creator);
-    const preview = multimediaMessagePreview(messageInfo);
+    const preview =
+      messageInfo.type === messageTypes.REACTION
+        ? reactionMessagePreview()
+        : multimediaMessagePreview(messageInfo);
     return `${creator} ${preview}`;
   }
   return robotextToRawString(robotextForMessageInfo(messageInfo, threadInfo));
diff --git a/lib/types/message-types.js b/lib/types/message-types.js
--- a/lib/types/message-types.js
+++ b/lib/types/message-types.js
@@ -327,7 +327,9 @@
   | CreateSidebarMessageInfo;
 export type PreviewableMessageInfo =
   | RobotextMessageInfo
-  | MultimediaMessageInfo;
+  | MultimediaMessageInfo
+  | ReactionMessageInfo;
+
 export type SidebarSourceMessageInfo = {
   +type: 17,
   +id: string,