diff --git a/src/pinky.c b/src/pinky.c
index ae36e0ff9..e7899f552 100644
--- a/src/pinky.c
+++ b/src/pinky.c
@@ -22,7 +22,9 @@
 #include <pwd.h>
 #include <stdio.h>
 
+#include <sys/types.h>
 #include "system.h"
+
 #include "error.h"
 #include "readutmp.h"
 #include "closeout.h"
diff --git a/src/uptime.c b/src/uptime.c
index eec73771a..779dff73b 100644
--- a/src/uptime.c
+++ b/src/uptime.c
@@ -21,10 +21,12 @@
 #include <getopt.h>
 #include <stdio.h>
 
+#include <sys/types.h>
+#include "system.h"
+
 #include "error.h"
 #include "long-options.h"
 #include "readutmp.h"
-#include "system.h"
 #include "closeout.h"
 
 /* The official name of this program (e.g., no `g' prefix).  */
diff --git a/src/users.c b/src/users.c
index 9a6d277d0..2c1b51995 100644
--- a/src/users.c
+++ b/src/users.c
@@ -21,10 +21,12 @@
 #include <getopt.h>
 #include <stdio.h>
 
+#include <sys/types.h>
+#include "system.h"
+
 #include "error.h"
 #include "long-options.h"
 #include "readutmp.h"
-#include "system.h"
 #include "closeout.h"
 
 /* The official name of this program (e.g., no `g' prefix).  */
diff --git a/src/who.c b/src/who.c
index a937365e1..06b01a7df 100644
--- a/src/who.c
+++ b/src/who.c
@@ -28,9 +28,11 @@
 #include <getopt.h>
 #include <stdio.h>
 
+#include <sys/types.h>
+#include "system.h"
+
 #include "error.h"
 #include "readutmp.h"
-#include "system.h"
 #include "closeout.h"
 
 /* The official name of this program (e.g., no `g' prefix).  */