diff --git a/spacy/pipeline.pyx b/spacy/pipeline.pyx
index e76fac3e4..eb3894969 100644
--- a/spacy/pipeline.pyx
+++ b/spacy/pipeline.pyx
@@ -681,7 +681,7 @@ class Tagger(Pipe):
                 idx += 1
         correct = self.model.ops.xp.array(correct, dtype='i')
         d_scores = scores - to_categorical(correct, nb_classes=scores.shape[1])
-        d_scores *= known_labels
+        d_scores *= self.ops.asarray(known_labels)
         loss = (d_scores**2).sum()
         d_scores = self.model.ops.unflatten(d_scores, [len(d) for d in docs])
         return float(loss), d_scores