diff --git a/sys/saul_reg/saul_reg.c b/sys/saul_reg/saul_reg.c
index 40f521ebf23ade024a690aa59a52dda8ca5827fa..729a7edf5352f5b821afb6223e260b2097a6162c 100644
--- a/sys/saul_reg/saul_reg.c
+++ b/sys/saul_reg/saul_reg.c
@@ -18,6 +18,7 @@
  * @}
  */
 
+#include <stddef.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <string.h>
diff --git a/sys/shell/commands/sc_saul_reg.c b/sys/shell/commands/sc_saul_reg.c
index 7922292ecacb4161a7f1fb59861913bdcf3ddfb4..b1f1adbf72177d2bcfe51e01e644ce90c3738408 100644
--- a/sys/shell/commands/sc_saul_reg.c
+++ b/sys/shell/commands/sc_saul_reg.c
@@ -19,6 +19,7 @@
  * @}
  */
 
+#include <stddef.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>