From 6771780d3f78ab3463fa7255516334059ed2721d Mon Sep 17 00:00:00 2001
From: Matthew Honnibal <honnibal+gh@gmail.com>
Date: Fri, 3 Nov 2017 01:54:34 +0100
Subject: [PATCH] Fix backprop of padding variable

---
 spacy/_ml.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/spacy/_ml.py b/spacy/_ml.py
index 4829631f4..0f9202603 100644
--- a/spacy/_ml.py
+++ b/spacy/_ml.py
@@ -150,7 +150,9 @@ class PrecomputableAffine(Model):
 
     def _backprop_padding(self, dY, ids):
         # (1, nF, nO, nP) += (nN, nF, nO, nP) where IDs (nN, nF) < 0
-        d_pad = dY * (ids.reshape((ids.shape[0], self.nF, 1, 1)) < 0.)
+        mask = ids < 0.
+        mask = mask.sum(axis=1)
+        d_pad = dY * mask.reshape((ids.shape[0], 1, 1))
         self.d_pad += d_pad.sum(axis=0)
         return dY, ids