diff --git a/lib/cpe/cryb_cpe_clone.c b/lib/cpe/cryb_cpe_clone.c
index dcb2c78..7fee092 100644
--- a/lib/cpe/cryb_cpe_clone.c
+++ b/lib/cpe/cryb_cpe_clone.c
@@ -30,6 +30,7 @@
 #include "cryb/impl.h"
 
 #include <stdlib.h>
+#include <unistd.h>
 #include <wchar.h>
 
 #include <cryb/wstring.h>
diff --git a/lib/cpe/cryb_cpe_destroy.c b/lib/cpe/cryb_cpe_destroy.c
index 73f5d15..8a8870e 100644
--- a/lib/cpe/cryb_cpe_destroy.c
+++ b/lib/cpe/cryb_cpe_destroy.c
@@ -30,6 +30,7 @@
 #include "cryb/impl.h"
 
 #include <stdlib.h>
+#include <unistd.h>
 #include <wchar.h>
 
 #include <cryb/wstring.h>
diff --git a/lib/cpe/cryb_cpe_new.c b/lib/cpe/cryb_cpe_new.c
index d1071bc..8e75cc7 100644
--- a/lib/cpe/cryb_cpe_new.c
+++ b/lib/cpe/cryb_cpe_new.c
@@ -30,6 +30,7 @@
 #include "cryb/impl.h"
 
 #include <stdlib.h>
+#include <unistd.h>
 #include <wchar.h>
 
 #include <cryb/wstring.h>