diff --git a/docs/conf.py b/docs/conf.py
index 7bd17033d..a785da8a8 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -29,7 +29,7 @@
 # -- 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/noxfile.py b/noxfile.py
index 09e7acbda..6a59685cd 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -171,7 +171,9 @@ 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(
diff --git a/synth.metadata b/synth.metadata
index 1ab561144..d5ec9eac2 100644
--- a/synth.metadata
+++ b/synth.metadata
@@ -19,21 +19,21 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "d302f93d7f47e2852e585ac35ab2d15585717ec0"
+        "sha": "ffcee7952b74f647cbb3ef021d95422f10816fca"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "d302f93d7f47e2852e585ac35ab2d15585717ec0"
+        "sha": "ffcee7952b74f647cbb3ef021d95422f10816fca"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "d302f93d7f47e2852e585ac35ab2d15585717ec0"
+        "sha": "ffcee7952b74f647cbb3ef021d95422f10816fca"
       }
     }
   ],