diff --git a/library/x509_crt.c b/library/x509_crt.c
index 4e7672e..730f6ef 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -22,6 +22,7 @@
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
 
 #include "mbedtls/x509_crt.h"
+#include "x509_internal.h"
 #include "mbedtls/error.h"
 #include "mbedtls/oid.h"
 #include "mbedtls/platform_util.h"