From 1a98e48b8e34d8a03cf8c91603a0a8c13e9e3381 Mon Sep 17 00:00:00 2001
From: Matthew Honnibal <honnibal+gh@gmail.com>
Date: Sat, 15 Apr 2017 13:35:01 +0200
Subject: [PATCH] Fix Stepwisestate'

---
 spacy/syntax/parser.pyx | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/spacy/syntax/parser.pyx b/spacy/syntax/parser.pyx
index 79969d1f4..b3281fe14 100644
--- a/spacy/syntax/parser.pyx
+++ b/spacy/syntax/parser.pyx
@@ -383,7 +383,7 @@ cdef class StepwiseState:
     def __init__(self, Parser parser, Doc doc, GoldParse gold=None):
         self.parser = parser
         self.doc = doc
-        if gold:
+        if gold is not None:
             self.gold = gold
         else:
             self.gold = GoldParse(doc)
@@ -427,6 +427,8 @@ cdef class StepwiseState:
         """
         Find the action-costs for the current state.
         """
+        if not self.gold:
+            raise ValueError("Can't set costs: No GoldParse provided")
         self.parser.moves.set_costs(self.eg.c.is_valid, self.eg.c.costs,
                 self.stcls, self.gold)
         costs = {}