diff --git a/doc/requirements.txt b/doc/requirements.txt
index 021350ac..71599d49 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,3 +1,8 @@
+# The order of packages is significant, because pip processes them in the order
+# of appearance. Changing the order has an impact on the overall integration
+# process, which may cause wedges in the gate later.
+
 openstackdocstheme>=1.11.0
-sphinx>=1.6.2 # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2;python_version>='3.4'  # BSD
 yasfb>=0.5.1
diff --git a/test-requirements.txt b/test-requirements.txt
index 3a8880f1..ed32ddd8 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,5 +1,10 @@
+# The order of packages is significant, because pip processes them in the order
+# of appearance. Changing the order has an impact on the overall integration
+# process, which may cause wedges in the gate later.
+
 openstackdocstheme>=1.11.0
-sphinx>=1.6.2 # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2;python_version>='3.4'  # BSD
 flake8
 yasfb>=0.5.1
 doc8>=0.6.0 # Apache-2.0