diff --git a/spacy/pos_util.py b/spacy/pos_util.py
index 039e6b15d..e5716665e 100644
--- a/spacy/pos_util.py
+++ b/spacy/pos_util.py
@@ -36,6 +36,8 @@ def read_gold(file_, tag_list, col):
     return golds
 
 def _encode_pos(tag, tag_ids, tag_list):
+    if tag == '-':
+        return 0
     if tag not in tag_ids:
         tag_ids[tag] = len(tag_list)
         tag_list.append(tag)