diff --git a/annif/backend/svc.py b/annif/backend/svc.py
index 5fbeccf5a..da8e46a86 100644
--- a/annif/backend/svc.py
+++ b/annif/backend/svc.py
@@ -56,7 +56,7 @@ def _corpus_to_texts_and_classes(self, corpus):
                 self.warning(
                     'training on a document with multiple subjects is not ' +
                     'supported by SVC; selecting one random subject.')
-            classes.append(list(doc.uris)[0])
+            classes.append(iter(doc.uris).next())
         return texts, classes
 
     def _train_classifier(self, veccorpus, classes):