diff --git a/cpu/cc2538/dev/ecc-algorithm.c b/cpu/cc2538/dev/ecc-algorithm.c
index 9e389375f..b67f1220c 100644
--- a/cpu/cc2538/dev/ecc-algorithm.c
+++ b/cpu/cc2538/dev/ecc-algorithm.c
@@ -40,6 +40,7 @@
 
 #include <limits.h>
 #include <stdio.h>
+#include <string.h>
 
 #include "dev/ecc-algorithm.h"
 #include "dev/ecc-driver.h"
diff --git a/cpu/cc2538/ieee-addr.c b/cpu/cc2538/ieee-addr.c
index f45e4210d..bd9c481a5 100644
--- a/cpu/cc2538/ieee-addr.c
+++ b/cpu/cc2538/ieee-addr.c
@@ -40,6 +40,7 @@
 #include "ieee-addr.h"
 
 #include <stdint.h>
+#include <string.h>
 /*---------------------------------------------------------------------------*/
 void
 ieee_addr_cpy_to(uint8_t *dst, uint8_t len)
diff --git a/cpu/cc253x/usb/common/cdc-acm/cdc-acm.c b/cpu/cc253x/usb/common/cdc-acm/cdc-acm.c
index 8c2808a13..444d6b0e3 100644
--- a/cpu/cc253x/usb/common/cdc-acm/cdc-acm.c
+++ b/cpu/cc253x/usb/common/cdc-acm/cdc-acm.c
@@ -4,6 +4,7 @@
 #include "usb-core.h"
 
 #include <stdio.h>
+#include <string.h>
 
 #ifdef DEBUG
 #define PRINTF(...) printf(__VA_ARGS__)