diff --git a/include/mbedtls/des.h b/include/mbedtls/des.h
index 6bfe654..29b96db 100644
--- a/include/mbedtls/des.h
+++ b/include/mbedtls/des.h
@@ -32,6 +32,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/platform_util.h"
 
 #include <stddef.h>
 #include <stdint.h>