diff --git a/spacy/serialize/bits.pxd b/spacy/serialize/bits.pxd
index 9c7593a92..d0b0a7fdd 100644
--- a/spacy/serialize/bits.pxd
+++ b/spacy/serialize/bits.pxd
@@ -20,4 +20,4 @@ cdef class BitArray:
     
     cdef int extend(self, uint64_t code, char n_bits) except -1
 
-    cdef uint32_t read32(self) except 0
+    cdef int32_t read32(self) except 0
diff --git a/spacy/serialize/bits.pyx b/spacy/serialize/bits.pyx
index 2f0fb30f6..71a198a46 100644
--- a/spacy/serialize/bits.pyx
+++ b/spacy/serialize/bits.pyx
@@ -65,7 +65,7 @@ cdef class BitArray:
                 self.i += 1
                 yield 1 if self.byte & (one << i) else 0
 
-    cdef uint32_t read32(self) except 0:
+    cpdef int32_t read32(self) except 0:
         cdef int start_byte = self.i // 8
 
         # TODO portability