diff --git a/noxfile.py b/noxfile.py
index 8b5bd202..b748fa1c 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -201,7 +201,7 @@ def docfx(session):
     session.install("-e", ".")
     # sphinx-docfx-yaml supports up to sphinx version 1.5.5.
     # https://github.com/docascode/sphinx-docfx-yaml/issues/97
-    session.install("sphinx==1.7.6", "alabaster", "recommonmark", "sphinx-docfx-yaml")
+    session.install("sphinx==1.5.5", "alabaster", "recommonmark", "sphinx-docfx-yaml")
 
     shutil.rmtree(os.path.join("docs", "_build"), ignore_errors=True)
     session.run(