diff --git a/global-requirements.txt b/global-requirements.txt
index 1d6f582af9..606f6ebc17 100644
--- a/global-requirements.txt
+++ b/global-requirements.txt
@@ -419,7 +419,7 @@ selenium>=2.50.1  # Apache-2.0
 # Blacklist setuptools 34.0.0-34.3.2 due to https://github.com/pypa/setuptools/issues/951
 # Blacklist setuptools 36.2.0 due to https://github.com/pypa/setuptools/issues/1086
 setuptools>=21.0.0,!=24.0.0,!=34.0.0,!=34.0.1,!=34.0.2,!=34.0.3,!=34.1.0,!=34.1.1,!=34.2.0,!=34.3.0,!=34.3.1,!=34.3.2,!=36.2.0  # PSF/ZPL
-sphinx>=1.6.2,!=1.6.6  # BSD
+sphinx>=1.6.2,!=1.6.6,<1.7.0  # BSD
 sphinx-testing>=0.7.2  # BSD License
 sphinxcontrib-actdiag>=0.8.5  # BSD
 sphinxcontrib-blockdiag>=1.5.4  # BSD
diff --git a/upper-constraints.txt b/upper-constraints.txt
index 6d6ca68b2a..47e6ef6ab2 100644
--- a/upper-constraints.txt
+++ b/upper-constraints.txt
@@ -351,7 +351,7 @@ seqdiag===0.9.5
 numpy===1.14.1
 repoze.who===2.3
 msgpack===0.5.6
-Sphinx===1.7.1
+Sphinx===1.6.5
 oslo.config===5.2.0
 tempest===18.0.0
 django-floppyforms===1.7.0