diff --git a/pyproject.toml b/pyproject.toml
index 1815fa6dd5d..2ada0c1c171 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -114,7 +114,6 @@ module = [
   "h5netcdf.*",
   "h5py.*",
   "iris.*",
-  "matplotlib.*",
   "mpl_toolkits.*",
   "nc_time_axis.*",
   "netCDF4.*",
diff --git a/xarray/tests/test_plot.py b/xarray/tests/test_plot.py
index a44b621a981..b302ad3af93 100644
--- a/xarray/tests/test_plot.py
+++ b/xarray/tests/test_plot.py
@@ -3406,3 +3406,13 @@ def test_plot1d_filtered_nulls() -> None:
         actual = pc.get_offsets().shape[0]
 
         assert expected == actual
+
+
+@requires_matplotlib
+def test_9155() -> None:
+    # A test for types from issue #9155
+
+    with figure_context():
+        data = xr.DataArray([1, 2, 3], dims=["x"])
+        fig, ax = plt.subplots(ncols=1, nrows=1)
+        data.plot(ax=ax)