Index: abi/include/abi/proc/uarg.h
===================================================================
--- abi/include/abi/proc/uarg.h	(revision aca642c01e1dd4f0528a1c47cbf0f2c426164564)
+++ abi/include/abi/proc/uarg.h	(revision 98a38791c78a67662e1d752dd4c6ac2ce413c18f)
@@ -36,4 +36,6 @@
 #define ABI_PROC_UARG_H_
 
+#include <stddef.h>
+
 /** Structure passed to uinit kernel thread as argument. */
 typedef struct uspace_arg {