diff --git a/ssl/ssl_cert.c b/ssl/ssl_cert.c
index aa074e4..258da8b 100644
--- a/ssl/ssl_cert.c
+++ b/ssl/ssl_cert.c
@@ -134,6 +134,7 @@
 #include <openssl/pem.h>
 #include <openssl/x509v3.h>
 #include <openssl/dh.h>
+#include <openssl/bn.h>
 #include "ssl_locl.h"
 
 int SSL_get_ex_data_X509_STORE_CTX_idx(void)