diff --git a/ssl/ssl_session.cc b/ssl/ssl_session.cc
index a680471..1830723 100644
--- a/ssl/ssl_session.cc
+++ b/ssl/ssl_session.cc
@@ -911,7 +911,7 @@
     return 0;
   }
 
-  assert(sizeof(session->sid_ctx) < 256);
+  static_assert(sizeof(session->sid_ctx) < 256, "sid_ctx_len does not fit");
   session->sid_ctx_length = (uint8_t)sid_ctx_len;
   OPENSSL_memcpy(session->sid_ctx, sid_ctx, sid_ctx_len);