diff --git a/lib/notmuch.h b/lib/notmuch.h
index c232c580..3974820c 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -686,6 +686,7 @@ notmuch_message_get_filename (notmuch_message_t *message);
 
 /* Message flags */
 typedef enum _notmuch_message_flag {
+    NOTMUCH_MSG_FLAG_MATCHING_SEARCH,
 } notmuch_message_flag_t;
 
 /* Get a value of a flag for the email corresponding to 'message'. */
diff --git a/lib/thread.cc b/lib/thread.cc
index 58d88c2d..9e4cb5c8 100644
--- a/lib/thread.cc
+++ b/lib/thread.cc
@@ -132,6 +132,7 @@ _thread_add_matched_message (notmuch_thread_t *thread,
 			     notmuch_message_t *message)
 {
     time_t date;
+    notmuch_message_t *hashed_message;
 
     date = notmuch_message_get_date (message);
 
@@ -142,6 +143,13 @@ _thread_add_matched_message (notmuch_thread_t *thread,
 	thread->newest = date;
 
     thread->matched_messages++;
+
+    if (g_hash_table_lookup_extended (thread->message_hash,
+			    notmuch_message_get_message_id (message), NULL,
+			    (void **) &hashed_message)) {
+	notmuch_message_set_flag (hashed_message,
+			NOTMUCH_MSG_FLAG_MATCHING_SEARCH, 1);
+    }
 }
 
 static void