diff --git a/include/metalsvm/mailbox.h b/include/metalsvm/mailbox.h
index 4dff4887..3ffb1d87 100644
--- a/include/metalsvm/mailbox.h
+++ b/include/metalsvm/mailbox.h
@@ -22,6 +22,7 @@
 
 #include <metalsvm/string.h>
 #include <metalsvm/mailbox_types.h>
+#include <metalsvm/tasks.h>
 #include <metalsvm/semaphore.h>
 
 #ifdef __cplusplus