diff --git a/oio-unix.c b/oio-unix.c
index aeeb2a20..42be55e6 100644
--- a/oio-unix.c
+++ b/oio-unix.c
@@ -21,15 +21,14 @@
 
 #include "oio.h"
 
+#include <stddef.h> /* NULL */
 #include <stdio.h> /* printf */
-
 #include <stdlib.h>
 #include <string.h> /* strerror */
 #include <errno.h>
 #include <assert.h>
 #include <unistd.h>
 #include <fcntl.h>
-
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
diff --git a/oio-unix.h b/oio-unix.h
index 3266bcc3..2c0cb13b 100644
--- a/oio-unix.h
+++ b/oio-unix.h
@@ -26,7 +26,6 @@
 
 #include "ev/ev.h"
 
-#include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <netinet/tcp.h>
diff --git a/oio.h b/oio.h
index 0d31133d..5cf0d28a 100644
--- a/oio.h
+++ b/oio.h
@@ -26,8 +26,7 @@
 #define OIO_VERSION_MINOR 1
 
 #include <stdint.h> /* int64_t */
-#include <stddef.h> /* size_t */
-
+#include <sys/types.h> /* size_t */
 
 typedef struct oio_err_s oio_err;
 typedef struct oio_handle_s oio_handle;