diff --git a/bwt_lite.c b/bwt_lite.c
index f7946f54..399cb323 100644
--- a/bwt_lite.c
+++ b/bwt_lite.c
@@ -1,6 +1,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
+#include <sys/types.h>
 #include "bwt_lite.h"
 
 #ifdef USE_MALLOC_WRAPPERS
diff --git a/bwtaln.c b/bwtaln.c
index 20b01cd3..5bc9f2ce 100644
--- a/bwtaln.c
+++ b/bwtaln.c
@@ -5,6 +5,7 @@
 #include <string.h>
 #include <time.h>
 #include <stdint.h>
+#include <sys/types.h>
 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif
diff --git a/bwtgap.c b/bwtgap.c
index 08bc1f48..3a68780c 100644
--- a/bwtgap.c
+++ b/bwtgap.c
@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/types.h>
 #include "bwtgap.h"
 #include "bwtaln.h"
 
diff --git a/kthread.c b/kthread.c
index 1b13494f..9a2ea503 100644
--- a/kthread.c
+++ b/kthread.c
@@ -1,5 +1,6 @@
 #include <pthread.h>
 #include <stdlib.h>
+#include <stdint.h>
 #include <limits.h>
 
 /************