diff --git a/orangecontrib/text/widgets/owimportdocuments.py b/orangecontrib/text/widgets/owimportdocuments.py
index 203cea9e9..eefeb2bbd 100644
--- a/orangecontrib/text/widgets/owimportdocuments.py
+++ b/orangecontrib/text/widgets/owimportdocuments.py
@@ -665,6 +665,8 @@ def __onReportProgress(self, arg):
     def add_features(self):
         self.Warning.clear()
         lemma, pos, ner = self.lemma_cb, self.pos_cb, self.ner_cb
+        if self.corpus is None:
+            return
         self.corpus = self.base_corpus.copy()
         if lemma:
             self.corpus.store_tokens(self.tokens)