diff --git a/agent/pseudotcp.c b/agent/pseudotcp.c
index 99aa709d18c1c5f1a0ab38737c3274b4b67755b6..46b8cf4200088b803d2b7cbd433fb061f456f98e 100644
--- a/agent/pseudotcp.c
+++ b/agent/pseudotcp.c
@@ -1961,7 +1961,7 @@ transmit(PseudoTcpSocket *self, SSegment *segment, guint32 now)
     PseudoTcpWriteResult wres;
 
     /* The packet must not have already been acknowledged. */
-    g_assert_cmpuint (segment->seq, >=, priv->snd_una);
+    g_assert_cmpuint (segment->seq - priv->snd_una, <=, 1024 * 1024 * 64);
 
     /* Write out the packet. */
     wres = packet(self, seq, flags,