diff --git a/doc/source/conf.py b/doc/source/conf.py
index eb772897a2..913262c958 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -73,7 +73,7 @@ extensions = ['sphinx.ext.autodoc',
               'sphinx.ext.viewcode',
               'sphinx.ext.todo',
               'sphinx.ext.coverage',
-              'sphinx.ext.viewcode',
+              'sphinx.ext.intersphinx',
               'sphinx.ext.doctest',
               'sphinxcontrib.apidoc',
               'openstackdocstheme',
@@ -85,6 +85,10 @@ extensions = ['sphinx.ext.autodoc',
               'ext.tablefromtext',
               'stevedore.sphinxext']
 
+intersphinx_mapping = {
+    'types_typedecorator': ('https://docs.sqlalchemy.org', None),
+}
+
 # policy sample file generation
 policy_generator_config_file = '../../etc/heat/heat-policy-generator.conf'
 sample_policy_basename = '_static/heat'