diff --git a/ckanext/dgu/lib/helpers.py b/ckanext/dgu/lib/helpers.py
index d02fdbd5ca112fc22991774a32ea2630d62e9abb..e6972c61262650650acca0872ef4123b040c1752 100644
--- a/ckanext/dgu/lib/helpers.py
+++ b/ckanext/dgu/lib/helpers.py
@@ -2914,6 +2914,8 @@ def detect_license_id(licence_str):
     :returns (license_id, is_wholely_identified)
     '''
     license_id = ''
+    if not licence_str:
+        return license_id, None
 
     global licence_regexes
     if licence_regexes is None: