diff --git a/setup.py b/setup.py
index 07a8828e5..25b7c00a7 100644
--- a/setup.py
+++ b/setup.py
@@ -24,7 +24,8 @@
                       "scipy >= 0.13",
                       "pydicom >= 0.9.9",
                       "matplotlib >= 1.3.1",
-                      "Pillow >= 2.5"],
+                      "Pillow >= 2.5",
+                      "sphinxcontrib-napoleon"],
     test_suite='tests._test_all',
     classifiers=[
         "Development Status :: 4 - Beta",