diff --git a/vlib/os/os.c.v b/vlib/os/os.c.v
index c50a1d4e57..9e1945e645 100644
--- a/vlib/os/os.c.v
+++ b/vlib/os/os.c.v
@@ -5,6 +5,10 @@ import strings
 #include <sys/stat.h> // #include <signal.h>
 #include <errno.h>
 
+$if freebsd {
+	#include <sys/sysctl.h>
+}
+
 pub const (
 	args = []string{}
 )