diff --git a/src/include/visibility.h b/src/include/visibility.h
index 1a956f02e8..4450c9495c 100644
--- a/src/include/visibility.h
+++ b/src/include/visibility.h
@@ -101,6 +101,9 @@
 
 #else // defined(ENABLE_LOCKSTEP_SCHEDULER)
 
+#include <stdlib.h>
+#include <unistd.h>
+
 #define system_usleep usleep
 #define system_sleep sleep
 #define system_clock_gettime clock_gettime