diff --git a/ckanext/harvest/harvesters/ckanharvester.py b/ckanext/harvest/harvesters/ckanharvester.py
index e8d5324d..878f20c5 100644
--- a/ckanext/harvest/harvesters/ckanharvester.py
+++ b/ckanext/harvest/harvesters/ckanharvester.py
@@ -38,7 +38,7 @@ def _get_content(self, url):
 
         user_agent = self.config.get('user_agent')
         if user_agent:
-            headers['User-Agent'] = user_agent
+            headers['User-Agent'] = str(user_agent)
 
         api_key = self.config.get('api_key')
         if api_key: