diff --git a/lib/notmuch.h b/lib/notmuch.h
index 505ad19f..9a196999 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -400,6 +400,8 @@ notmuch_query_set_sort (notmuch_query_t *query, notmuch_sort_t sort);
  * notmuch_threads_t object. (For consistency, we do provide a
  * notmuch_threads_destroy function, but there's no good reason
  * to call it if the query is about to be destroyed).
+ *
+ * If a Xapian exception occurs this function will return NULL.
  */
 notmuch_threads_t *
 notmuch_query_search_threads (notmuch_query_t *query);
diff --git a/lib/query.cc b/lib/query.cc
index d241dc1d..59f4011b 100644
--- a/lib/query.cc
+++ b/lib/query.cc
@@ -249,6 +249,10 @@ notmuch_query_search_threads (notmuch_query_t *query)
 					      free, NULL);
 
     threads->messages = notmuch_query_search_messages (query);
+    if (threads->messages == NULL) {
+	    talloc_free (threads);
+	    return NULL;
+    }
 
     threads->thread_id = NULL;