diff --git a/src/apps/relay/mainrelay.h b/src/apps/relay/mainrelay.h
index ecf8a140..406bea89 100644
--- a/src/apps/relay/mainrelay.h
+++ b/src/apps/relay/mainrelay.h
@@ -80,6 +80,7 @@
 #include <openssl/aes.h>
 #include <openssl/err.h>
 #include <openssl/pem.h>
+#include <openssl/modes.h>
 
 #ifdef __cplusplus
 extern "C" {