diff --git a/spacy/ml/models/coref_util.py b/spacy/ml/models/coref_util.py
index 7ace3afcf..f578f1580 100644
--- a/spacy/ml/models/coref_util.py
+++ b/spacy/ml/models/coref_util.py
@@ -143,8 +143,7 @@ def get_candidate_mentions(
         si = sentence_map[tok.i]  # sentence index
         for ii in range(1, max_span_width):
             ei = tok.i + ii  # end index
-
-            if ei > len(doc) or sentence_map[ei] != si:
+            if ei >= len(doc) or sentence_map[ei] != si:
                 continue
 
             begins.append(tok.i)