diff --git a/spacy/gold/align.pyx b/spacy/gold/align.pyx
index 49e8aaa98..80ba0346a 100644
--- a/spacy/gold/align.pyx
+++ b/spacy/gold/align.pyx
@@ -2,7 +2,7 @@ import numpy
 from ..errors import Errors, AlignmentError
 
 
-class Alignment:
+cdef class Alignment:
     def __init__(self, spacy_words, gold_words):
         # Do many-to-one alignment for misaligned tokens.
         # If we over-segment, we'll have one gold word that covers a sequence