diff --git a/synthtool/gcp/templates/python_library/docs/conf.py.j2 b/synthtool/gcp/templates/python_library/docs/conf.py.j2
index 654292bc6..6ce53ce77 100644
--- a/synthtool/gcp/templates/python_library/docs/conf.py.j2
+++ b/synthtool/gcp/templates/python_library/docs/conf.py.j2
@@ -29,7 +29,7 @@ __version__ = "{{ metadata['version'] }}"
 # -- General configuration ------------------------------------------------
 
 # If your documentation needs a minimal Sphinx version, state it here.
-needs_sphinx = "1.6.3"
+needs_sphinx = "1.5.5"
 
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
diff --git a/synthtool/gcp/templates/python_library/noxfile.py.j2 b/synthtool/gcp/templates/python_library/noxfile.py.j2
index a9275496e..5c9ac730c 100644
--- a/synthtool/gcp/templates/python_library/noxfile.py.j2
+++ b/synthtool/gcp/templates/python_library/noxfile.py.j2
@@ -194,7 +194,9 @@ def docfx(session):
     """Build the docfx yaml files for this library."""
 
     session.install("-e", ".")
-    session.install("sphinx", "alabaster", "recommonmark", "sphinx-docfx-yaml")
+    # sphinx-docfx-yaml supports up to sphinx version 1.5.5.
+    # https://github.com/docascode/sphinx-docfx-yaml/issues/97
+    session.install("sphinx==1.5.5", "alabaster", "recommonmark", "sphinx-docfx-yaml")
 
     shutil.rmtree(os.path.join("docs", "_build"), ignore_errors=True)
     session.run(