diff --git a/scopesim/effects/surface_list.py b/scopesim/effects/surface_list.py
index d17322a2..252c5203 100644
--- a/scopesim/effects/surface_list.py
+++ b/scopesim/effects/surface_list.py
@@ -156,7 +156,7 @@ def plot(self, which="x", wavelength=None, *, axes=None, **kwargs):
 
         """
         if axes is None:
-            fig, axes = figure_factory(len(which), 1)
+            fig, axes = figure_factory(len(which), 1, iterable_axes=True)
         else:
             fig = axes.figure
             self._axes_guard(which, axes)
diff --git a/scopesim/effects/ter_curves.py b/scopesim/effects/ter_curves.py
index 51058c7e..cfd9a548 100644
--- a/scopesim/effects/ter_curves.py
+++ b/scopesim/effects/ter_curves.py
@@ -186,8 +186,7 @@ def plot(self, which="x", wavelength=None, *, axes=None, **kwargs):
 
         """
         if axes is None:
-            fig, axes = figure_factory(len(which), 1)
-            # figsize=(10, 5)
+            fig, axes = figure_factory(len(which), 1, iterable_axes=True)
         else:
             fig = axes.figure
             _guard_plot_axes(which, axes)
@@ -627,8 +626,7 @@ def plot(self, which="x", wavelength=None, *, axes=None, **kwargs):
 
         """
         if axes is None:
-            fig, axes = figure_factory(len(which), 1)
-            # figsize=(10, 5)
+            fig, axes = figure_factory(len(which), 1, iterable_axes=True)
         else:
             fig = axes.figure
             _guard_plot_axes(which, axes)
diff --git a/scopesim/utils.py b/scopesim/utils.py
index 19f0d6db..d653b40c 100644
--- a/scopesim/utils.py
+++ b/scopesim/utils.py
@@ -1032,7 +1032,10 @@ def close_loop(iterable: Iterable) -> Generator:
 
 def figure_factory(nrows=1, ncols=1, **kwargs):
     """Default way to init fig and ax, to easily modify later."""
+    iterable_axes = kwargs.pop("iterable_axes", False)
     fig, ax = plt.subplots(nrows, ncols, **kwargs)
+    if iterable_axes and not isinstance(ax, Iterable):
+        ax = (ax,)
     return fig, ax