diff --git a/src/kernel/libroot/posix/unistd/ttyname.c b/src/kernel/libroot/posix/unistd/ttyname.c
index 3e9439d38c..1b94450f02 100644
--- a/src/kernel/libroot/posix/unistd/ttyname.c
+++ b/src/kernel/libroot/posix/unistd/ttyname.c
@@ -8,6 +8,7 @@
 #include <unistd.h>
 #include <dirent.h>
 #include <sys/stat.h>
+#include <sys/param.h>
 
 
 /* the root directory in /dev where all tty devices reside */