diff --git a/library/x509_create.c b/library/x509_create.c
index 7621698..e5ade5d 100644
--- a/library/x509_create.c
+++ b/library/x509_create.c
@@ -11,6 +11,7 @@
 
 #include "mbedtls/asn1write.h"
 #include "mbedtls/error.h"
+#include "mbedtls/oid.h"
 #include "x509_oid.h"
 
 #include <string.h>