diff --git a/doc/requirements.txt b/doc/requirements.txt
index ce60719..95b6568 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,5 +1,5 @@
 sphinx!=1.6.6,!=1.6.7,>=1.6.2 # BSD
 openstackdocstheme>=1.18.1  # Apache-2.0
-os-api-ref>=1.0.0 # Apache-2.0
+os-api-ref>=1.6.0 # Apache-2.0
 # releasenotes
 reno>=2.5.0 # Apache-2.0