diff --git a/src/cmsplugin_blurp/renderers/data_source.py b/src/cmsplugin_blurp/renderers/data_source.py
index 76076ac..ccdfb56 100644
--- a/src/cmsplugin_blurp/renderers/data_source.py
+++ b/src/cmsplugin_blurp/renderers/data_source.py
@@ -195,7 +195,9 @@ class Data(object):
         self.async = source.get('async', False)
         self.timeout = source.get('timeout', 10)
         self.auth_mech = source.get('auth_mech')
-        self.signature_key = source.get('signature_key').encode('ascii')
+        self.signature_key = None
+        if source.get('signature_key'):
+            self.signature_key = source.get('signature_key').encode('ascii')
         self.parser_type = source.get('parser_type', 'raw')
         self.content_type = source.get('content_type', self.MAPPING[self.parser_type])
         self.user_context = source.get('user_context',