diff --git a/src/api/netdb.c b/src/api/netdb.c
index 8cff3bc6..8aa237f4 100644
--- a/src/api/netdb.c
+++ b/src/api/netdb.c
@@ -42,6 +42,9 @@
 #include "lwip/ip_addr.h"
 #include "lwip/api.h"
 
+#include <string.h>
+#include <stdlib.h>
+
 /** helper struct for gethostbyname_r to access the char* buffer */
 struct gethostbyname_r_helper {
   struct ip_addr *addrs;
diff --git a/src/core/ipv4/ip.c b/src/core/ipv4/ip.c
index 18a8e812..7e404a9f 100644
--- a/src/core/ipv4/ip.c
+++ b/src/core/ipv4/ip.c
@@ -56,6 +56,8 @@
 #include "lwip/stats.h"
 #include "arch/perf.h"
 
+#include <string.h>
+
 /**
  * The interface that provided the packet for the current callback
  * invocation.