diff --git a/ssl/ssl_session.c b/ssl/ssl_session.c
index 96daec0..345aca2 100644
--- a/ssl/ssl_session.c
+++ b/ssl/ssl_session.c
@@ -133,6 +133,8 @@
  * OTHER ENTITY BASED ON INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS OR
  * OTHERWISE. */
 
+#include <openssl/ssl.h>
+
 #include <assert.h>
 #include <stdio.h>
 #include <string.h>