diff --git a/subprojects/test.h/test.h b/subprojects/test.h/test.h
index 5211dc1..5f25bfc 100644
--- a/subprojects/test.h/test.h
+++ b/subprojects/test.h/test.h
@@ -12,6 +12,7 @@
     defined(__NetBSD__) || defined(__OpenBSD__)
 #define USE_SYSCTL_FOR_ARGS 1
 #include <sys/sysctl.h>
+#include <sys/types.h>
 #include <unistd.h>        // getpid
 #endif