diff --git a/processors/metrics/url_titles.py b/processors/metrics/url_titles.py
index e32e3538d..75ebd12d0 100644
--- a/processors/metrics/url_titles.py
+++ b/processors/metrics/url_titles.py
@@ -145,7 +145,7 @@ def process(self):
         self.dataset.update_status("Finding URLs in dataset")
         for item in self.source_dataset.iterate_items(self):
             # combine column contents that we need to extract URLs from
-            source_text = " ".join([item[column] for column in columns])
+            source_text = " ".join([str(item[column]) for column in columns])
             urls = ural.urls_from_text(source_text)
 
             for url in urls: