diff --git a/piker/data/_compression.py b/piker/data/_compression.py
index aed1d7d3bf..e6111fcab6 100644
--- a/piker/data/_compression.py
+++ b/piker/data/_compression.py
@@ -35,13 +35,17 @@
 log = get_logger(__name__)
 
 
-def hl2mxmn(ohlc: np.ndarray) -> np.ndarray:
+def hl2mxmn(
+    ohlc: np.ndarray,
+    index_field: str = 'index',
+
+) -> np.ndarray:
     '''
     Convert a OHLC struct-array containing 'high'/'low' columns
     to a "joined" max/min 1-d array.
 
     '''
-    index = ohlc['index']
+    index = ohlc[index_field]
     hls = ohlc[[
         'low',
         'high',
@@ -109,6 +113,7 @@ def trace_hl(
 def ohlc_flatten(
     ohlc: np.ndarray,
     use_mxmn: bool = True,
+    index_field: str = 'index',
 
 ) -> tuple[np.ndarray, np.ndarray]:
     '''
@@ -117,7 +122,7 @@ def ohlc_flatten(
     evenly (by 0.5 steps) over each index.
 
     '''
-    index = ohlc['index']
+    index = ohlc[index_field]
 
     if use_mxmn:
         # traces a line optimally over highs to lows
diff --git a/piker/ui/_curve.py b/piker/ui/_curve.py
index 663b328f70..8df1cda059 100644
--- a/piker/ui/_curve.py
+++ b/piker/ui/_curve.py
@@ -360,11 +360,12 @@ def draw_last_datum(
         render_data: np.ndarray,
         reset: bool,
         array_key: str,
+        index_field: str,
 
     ) -> None:
         # default line draw last call
         # with self.reset_cache():
-        x = render_data['index']
+        x = render_data[index_field]
         y = render_data[array_key]
 
         # draw the "current" step graphic segment so it
@@ -391,10 +392,11 @@ def draw_last_datum(
         render_data: np.ndarray,
         reset: bool,
         array_key: str,
+        index_field: str,
 
     ) -> None:
         lasts = src_data[-2:]
-        x = lasts['index']
+        x = lasts[index_field]
         y = lasts['close']
 
         # draw the "current" step graphic segment so it
@@ -421,6 +423,7 @@ def draw_last_datum(
         render_data: np.ndarray,
         reset: bool,
         array_key: str,
+        index_field: str,
 
         w: float = 0.5,
 
@@ -429,7 +432,7 @@ def draw_last_datum(
         # TODO: remove this and instead place all step curve
         # updating into pre-path data render callbacks.
         # full input data
-        x = src_data['index']
+        x = src_data[index_field]
         y = src_data[array_key]
 
         x_last = x[-1]
@@ -458,9 +461,3 @@ def sub_paint(
         # p.drawLines(*tuple(filter(bool, self._last_step_lines)))
         # p.drawRect(self._last_step_rect)
         p.fillRect(self._last_step_rect, self._brush)
-
-    # def sub_br(
-    #     self,
-    #     parent_br: QRectF | None = None,
-    # ) -> QRectF:
-    #     return self._last_step_rect
diff --git a/piker/ui/_ohlc.py b/piker/ui/_ohlc.py
index 2ce23d30fe..98ffcb85ba 100644
--- a/piker/ui/_ohlc.py
+++ b/piker/ui/_ohlc.py
@@ -59,8 +59,8 @@ def bar_from_ohlc_row(
     OHLC "bar" for use in the "last datum" of a series.
 
     '''
-    open, high, low, close, index = row[
-        ['open', 'high', 'low', 'close', 'index']]
+    open, high, low, close, index = row  #[fields]
+        # ['open', 'high', 'low', 'close', 'index']]
 
     # TODO: maybe consider using `QGraphicsLineItem` ??
     # gives us a ``.boundingRect()`` on the objects which may make
@@ -217,30 +217,33 @@ def draw_last_datum(
         render_data: np.ndarray,
         reset: bool,
         array_key: str,
+        index_field: str,
 
+    ) -> None:
+
+        # relevant fields
         fields: list[str] = [
-            'index',
             'open',
             'high',
             'low',
             'close',
-        ],
-
-    ) -> None:
-
-        # relevant fields
+            index_field,
+        ]
         ohlc = src_data[fields]
         # last_row = ohlc[-1:]
 
         # individual values
-        last_row = i, o, h, l, last = ohlc[-1]
+        last_row = o, h, l, last, i = ohlc[-1]
 
         # times = src_data['time']
         # if times[-1] - times[-2]:
         #     breakpoint()
 
         # generate new lines objects for updatable "current bar"
-        self._last_bar_lines = bar_from_ohlc_row(last_row)
+        self._last_bar_lines = bar_from_ohlc_row(
+            last_row,
+            # fields,
+        )
 
         # assert i == graphics.start_index - 1
         # assert i == last_index
@@ -270,4 +273,4 @@ def draw_last_datum(
             # because i've seen it do this to bars i - 3 back?
 
         # return ohlc['time'], ohlc['close']
-        return ohlc['index'], ohlc['close']
+        return ohlc[index_field], ohlc['close']