diff --git a/numcodecs/compat_ext.pyx b/numcodecs/compat_ext.pyx
index f6462b89..f57e3cfd 100644
--- a/numcodecs/compat_ext.pyx
+++ b/numcodecs/compat_ext.pyx
@@ -12,7 +12,7 @@ from .compat import ensure_contiguous_ndarray
 cdef class Buffer:
     """Convenience class for buffer interface."""
 
-    def __cinit__(self, obj, flags):
+    def __cinit__(self, obj, int flags):
         PyObject_GetBuffer(obj, &(self.buffer), flags)
         self.acquired = True
         self.ptr = <char *> self.buffer.buf