diff --git a/quartical/apps/plotter.py b/quartical/apps/plotter.py
index 35f18977..45577001 100644
--- a/quartical/apps/plotter.py
+++ b/quartical/apps/plotter.py
@@ -193,6 +193,9 @@ def to_plot_dict(xdsl, iter_attrs):
 
 
 def _plot(group, xds, args):
+    # get rid of question marks
+    qstrip = lambda x: x.replace('?', 'N/A')
+    group = tuple(map(qstrip, group))
 
     xds = xds.compute(scheduler="single-threaded")