--- a/src/pyams_default_theme/shared/common/interfaces.py	Thu Jan 03 15:26:36 2019 +0100
+++ b/src/pyams_default_theme/shared/common/interfaces.py	Thu Jan 03 15:30:47 2019 +0100
@@ -13,6 +13,7 @@
 __docformat__ = 'restructuredtext'
 
 from zope.contentprovider.interfaces import IContentProvider
+from zope.interface import Interface
 
 from pyams_portal.interfaces import IPortletSettings
 
@@ -31,3 +32,7 @@
 
 class ICustomContentSpecificitiesParagraphRenderer(IContentProvider):
     """Custom content specificities paragraph renderer"""
+
+
+class ISharedContentHeadViewletManager(Interface):
+    """Shared content head viewlet manager marker interface"""