From 44fbdc7260a08793bc0daae6eff534d7570549f7 Mon Sep 17 00:00:00 2001
From: Matthew Honnibal <honnibal@gmail.com>
Date: Sun, 8 Nov 2015 16:19:12 +0100
Subject: [PATCH] * Fix bug in NER transition system, that sometimes left no
 valid moves

---
 spacy/syntax/ner.pyx | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/spacy/syntax/ner.pyx b/spacy/syntax/ner.pyx
index c23fa8148..806050dc4 100644
--- a/spacy/syntax/ner.pyx
+++ b/spacy/syntax/ner.pyx
@@ -170,6 +170,9 @@ cdef class Begin:
             return False
         elif preset_ent_iob == 3 and st.B_(0).ent_type != label:
             return False
+        # If the next word is B or O, we can't B now
+        elif st.B_(1).ent_iob == 2 or st.B_(1).ent_iob == 3:
+            return False
         # Don't allow entities to extend across sentence boundaries
         elif st.B_(1).sent_start:
             return False