diff --git a/docs/release.rst b/docs/release.rst
index 018f1658..12b186ed 100644
--- a/docs/release.rst
+++ b/docs/release.rst
@@ -32,6 +32,9 @@ Fixes
 * Fix ``const`` discard warnings in ``fletcher32``.
   By :user:`John Kirkham <jakirkham>`, :issue:`728`
 
+* Add ``#ifdef`` guard around ``PyBytes_RESIZE``.
+  By :user:`John Kirkham <jakirkham>`, :issue:`731`
+
 Maintenance
 ~~~~~~~~~~~
 
diff --git a/numcodecs/compat_ext.pxd b/numcodecs/compat_ext.pxd
index 436c23fb..129c1d86 100644
--- a/numcodecs/compat_ext.pxd
+++ b/numcodecs/compat_ext.pxd
@@ -3,7 +3,9 @@
 
 cdef extern from *:
     """
+    #ifndef PyBytes_RESIZE
     #define PyBytes_RESIZE(b, n) _PyBytes_Resize(&b, n)
+    #endif
     """
     int PyBytes_RESIZE(object b, Py_ssize_t n) except -1