diff --git a/Include/unicodeobject.h b/Include/unicodeobject.h
index c2360d3..ca17b48 100644
--- a/Include/unicodeobject.h
+++ b/Include/unicodeobject.h
@@ -373,7 +373,7 @@
    in most situations is solely ASCII whitespace, we optimize for the common
    case by using a quick look-up table with an inlined check.
  */
-extern const unsigned char _Py_ascii_whitespace[];
+PyAPI_DATA(const unsigned char) _Py_ascii_whitespace[];
 
 #define Py_UNICODE_ISSPACE(ch) \
 	((ch) < 128U ? _Py_ascii_whitespace[(ch)] : _PyUnicode_IsWhitespace(ch))