diff --git a/tests/test-ovn.c b/tests/test-ovn.c
index 60b87de..4ad3697 100644
--- a/tests/test-ovn.c
+++ b/tests/test-ovn.c
@@ -974,6 +974,9 @@ test_tree_shape_exhaustively(struct expr *expr, struct shash *symtab,
 }
 
 #ifndef _WIN32
+#ifndef WAIT_ANY
+#define WAIT_ANY   (-1)
+#endif
 static void
 wait_pid(pid_t *pids, int *n)
 {