diff --git a/Python/marshal.c b/Python/marshal.c
index b3986a80a6c..94e6d3a7620 100644
--- a/Python/marshal.c
+++ b/Python/marshal.c
@@ -33,6 +33,7 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 #include "marshal.h"
 
 #include <errno.h>
+extern int errno;
 
 #define TYPE_NULL	'0'
 #define TYPE_NONE	'N'