diff --git a/piker/fsp/_engine.py b/piker/fsp/_engine.py
index 357934d8..93bf0388 100644
--- a/piker/fsp/_engine.py
+++ b/piker/fsp/_engine.py
@@ -114,7 +114,7 @@ async def fsp_compute(
 
     # HISTORY COMPUTE PHASE
     # conduct a single iteration of fsp with historical bars input
-    # and get historical output, pack into 
+    # and get historical output.
     history_output: Union[
         dict[str, np.ndarray],  # multi-output case
         np.ndarray,  # single output case
@@ -415,12 +415,12 @@ async def cascade(
                     return not (
                         # the source is likely backfilling and we must
                         # sync history calculations
-                        len_diff > 2 or
+                        len_diff > 2
 
                         # we aren't step synced to the source and may be
                         # leading/lagging by a step
-                        step_diff > 1 or
-                        step_diff < 0
+                        or step_diff > 1
+                        or step_diff < 0
                     ), step_diff, len_diff
 
                 async def poll_and_sync_to_step(
@@ -485,15 +485,24 @@ async def cascade(
                         else:
                             last = array[-1:].copy()
 
-                        # sync with source time step
-                        src_t = src.array['time'][-1]
-                        last['time'] = src_t
-
                         dst.push(last)
 
-                        # dst_t = dst.array['time'][-1]
-                        # print(
-                        #     f'{dst.token}\n'
-                        #     f'src: {src_t}\n'
-                        #     f'dst: {dst_t}\n'
-                        # )
+                        # sync with source buffer's time step
+                        src_l2 = src.array[-2:]
+                        src_li, src_lt = src_l2[-1][['index', 'time']]
+                        src_2li, src_2lt = src_l2[-2][['index', 'time']]
+                        dst._array['time'][src_li] = src_lt
+                        dst._array['time'][src_2li] = src_2lt
+
+                        # last2 = dst.array[-2:]
+                        # if (
+                        #     last2[-1]['index'] != src_li
+                        #     or last2[-2]['index'] != src_2li
+                        # ):
+                        #     dstl2 = list(last2)
+                        #     srcl2 = list(src_l2)
+                        #     print(
+                        #         # f'{dst.token}\n'
+                        #         f'src: {srcl2}\n'
+                        #         f'dst: {dstl2}\n'
+                        #     )