diff --git a/src/buffer.c b/src/buffer.c
index 001e011..58e33d5 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -1,4 +1,5 @@
 #include <string.h>
+#include <stdlib.h>
 #include "ocl.h"
 
 #define USE_RINTERNALS 1
diff --git a/src/wrap.c b/src/wrap.c
index 7fe9e55..baa3af5 100644
--- a/src/wrap.c
+++ b/src/wrap.c
@@ -1,4 +1,5 @@
 #include "ocl.h"
+#include <stdlib.h>
 
 #include <Rinternals.h>
 #include <R_ext/Visibility.h>