diff --git a/ssl/d1_both.c b/ssl/d1_both.c
index 9fa46b1..1acb3ce 100644
--- a/ssl/d1_both.c
+++ b/ssl/d1_both.c
@@ -111,6 +111,8 @@
  * copied and put under another distribution licence
  * [including the GNU Public Licence.] */
 
+#include <openssl/ssl.h>
+
 #include <assert.h>
 #include <limits.h>
 #include <stdio.h>