diff --git a/spacy/syntax/nn_parser.pyx b/spacy/syntax/nn_parser.pyx
index fb7099022..5d6f51538 100644
--- a/spacy/syntax/nn_parser.pyx
+++ b/spacy/syntax/nn_parser.pyx
@@ -633,10 +633,9 @@ cdef class Parser:
         xp = get_array_module(d_tokvecs)
         for ids, d_vector, bp_vector in backprops:
             d_state_features = bp_vector(d_vector, sgd=sgd)
-            mask = ids >= 0
-            indices = xp.nonzero(mask)
-            self.model[0].ops.scatter_add(d_tokvecs, ids[indices],
-                d_state_features[indices])
+            mask = (ids >= 0).reshape((ids.shape[0], ids.shape[1], 1))
+            self.model[0].ops.scatter_add(d_tokvecs, ids,
+                d_state_features * mask)
 
     @property
     def move_names(self):