diff --git a/openmc/model/model.py b/openmc/model/model.py
index 0ea6db8db88..ffad8f503c7 100644
--- a/openmc/model/model.py
+++ b/openmc/model/model.py
@@ -820,14 +820,14 @@ def plot(
 
         Parameters
         ----------
-        n_samples : dict
+        n_samples : int, optional
             The number of source particles to sample and add to plot. Defaults
             to None which doesn't plot any particles on the plot.
         plane_tolerance: float
             When plotting a plane the source locations within the plane +/-
             the plane_tolerance will be included and those outside of the
             plane_tolerance will not be shown
-        source_kwargs : dict
+        source_kwargs : dict, optional
             Keyword arguments passed to :func:`matplotlib.pyplot.scatter`.
         **kwargs
             Keyword arguments passed to :func:`openmc.Universe.plot`