--- a/src/pyams_content/component/extfile/zmi/widget.py	Wed Oct 17 14:40:14 2018 +0200
+++ b/src/pyams_content/component/extfile/zmi/widget.py	Wed Oct 17 15:44:50 2018 +0200
@@ -13,7 +13,9 @@
 __docformat__ = 'restructuredtext'
 
 from z3c.form.browser.text import TextWidget
+from z3c.form.interfaces import DISPLAY_MODE, INPUT_MODE, ITextWidget
 from z3c.form.widget import FieldWidget
+from zope.interface import implementer_only
 
 from pyams_content.component.extfile.interfaces import IExtFileManagerInfo
 from pyams_form.interfaces import IFormLayer
@@ -22,8 +24,13 @@
 from pyams_i18n.widget import I18nTextLineWidget
 
 
-@widgettemplate_config(mode='input', template='templates/extfile-title-input.pt', layer=IFormLayer)
-@widgettemplate_config(mode='display', template='templates/extfile-title-display.pt', layer=IFormLayer)
+class IExtFileTitleFieldWidget(ITextWidget):
+    """external file title field widget interface"""
+
+
+@widgettemplate_config(mode=INPUT_MODE, template='templates/extfile-title-input.pt', layer=IFormLayer)
+@widgettemplate_config(mode=DISPLAY_MODE, template='templates/extfile-title-display.pt', layer=IFormLayer)
+@implementer_only(IExtFileTitleFieldWidget)
 class ExtFileTitleWidget(TextWidget):
     """External file title widget"""