diff --git a/libc/private/bionic_futex.h b/libc/private/bionic_futex.h
index bd2bd36..401577a 100644
--- a/libc/private/bionic_futex.h
+++ b/libc/private/bionic_futex.h
@@ -34,6 +34,7 @@
 #include <stddef.h>
 #include <sys/cdefs.h>
 #include <sys/syscall.h>
+#include <unistd.h>
 
 __BEGIN_DECLS