diff --git a/lib/mpl_toolkits/mplot3d/art3d.py b/lib/mpl_toolkits/mplot3d/art3d.py
index d38fa862b69e..c8b068165f7b 100644
--- a/lib/mpl_toolkits/mplot3d/art3d.py
+++ b/lib/mpl_toolkits/mplot3d/art3d.py
@@ -758,7 +758,7 @@ def set_alpha(self, alpha):
                 raise TypeError('alpha must be a float or None')
         artist.Artist.set_alpha(self, alpha)
         try:
-            self._facecolors = mcolors.to_rgba_array(
+            self._facecolors3d = mcolors.to_rgba_array(
                 self._facecolors3d, self._alpha)
         except (AttributeError, TypeError, IndexError):
             pass
diff --git a/lib/mpl_toolkits/tests/baseline_images/test_mplot3d/poly3dcollection_alpha.png b/lib/mpl_toolkits/tests/baseline_images/test_mplot3d/poly3dcollection_alpha.png
new file mode 100644
index 000000000000..6081c5a7e19c
Binary files /dev/null and b/lib/mpl_toolkits/tests/baseline_images/test_mplot3d/poly3dcollection_alpha.png differ
diff --git a/lib/mpl_toolkits/tests/test_mplot3d.py b/lib/mpl_toolkits/tests/test_mplot3d.py
index 92b4031a6e85..57998c36dcf4 100644
--- a/lib/mpl_toolkits/tests/test_mplot3d.py
+++ b/lib/mpl_toolkits/tests/test_mplot3d.py
@@ -454,6 +454,24 @@ def test_poly_collection_2d_to_3d_empty():
     assert poly.get_paths() == []
 
 
+@image_comparison(baseline_images=['poly3dcollection_alpha'],
+                  remove_text=True, extensions=['png'])
+def test_poly3dcollection_alpha():
+    fig = plt.figure()
+    ax = fig.gca(projection='3d')
+
+    poly1 = np.array([[0, 0, 1], [0, 1, 1], [0, 0, 0]], float)
+    poly2 = np.array([[0, 1, 1], [1, 1, 1], [1, 1, 0]], float)
+    c1 = art3d.Poly3DCollection([poly1], linewidths=3, edgecolor='k',
+                                facecolor=(0.5, 0.5, 1), closed=True)
+    c1.set_alpha(0.5)
+    c2 = art3d.Poly3DCollection([poly2], linewidths=3, edgecolor='k',
+                                facecolor=(1, 0.5, 0.5), closed=False)
+    c2.set_alpha(0.5)
+    ax.add_collection3d(c1)
+    ax.add_collection3d(c2)
+
+
 @image_comparison(baseline_images=['axes3d_labelpad'], extensions=['png'])
 def test_axes3d_labelpad():
     from matplotlib import rcParams