diff --git a/cluster.c b/cluster.c
index 12f1794..e31e234 100644
--- a/cluster.c
+++ b/cluster.c
@@ -48,6 +48,10 @@ int forked = 0;				// Sanity check: CLI must not diddle with heartbeat table
 
 #define MAX_HEART_SIZE (8192)	// Maximum size of heartbeat packet. Must be less than max IP packet size :)
 #define MAX_CHANGES  (MAX_HEART_SIZE/(sizeof(sessiont) + sizeof(int) ) - 2)	// Assumes a session is the biggest type!
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112
+_Static_assert(sizeof(sessiont) >= sizeof(tunnelt));
+_Static_assert(sizeof(sessiont) >= sizeof(bundlet));
+#endif
 
 static struct {
 	int type;