diff --git a/piker/data/flows.py b/piker/data/flows.py
index d281a0bf..2b3b666e 100644
--- a/piker/data/flows.py
+++ b/piker/data/flows.py
@@ -245,7 +245,7 @@ class Flume(Struct):
             return array['index'][mask][0]
 
         # just the latest index
-        array['index'][-1]
+        return array['index'][-1]
 
     def slice_from_time(
         self,