diff --git a/Modules/expat/xmltok.c b/Modules/expat/xmltok.c
index 6b415d83972..fa35de71324 100644
--- a/Modules/expat/xmltok.c
+++ b/Modules/expat/xmltok.c
@@ -30,6 +30,7 @@
    USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
+#include <pyconfig.h>
 #include <stddef.h>
 #include <string.h>  /* memcpy */