diff --git a/ChangeLog b/ChangeLog
index 274e22381..14a9db1ce 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -13,6 +13,10 @@
      minor tweak: when generating the hex fingerprint, give strlcat the full
      bound to the buffer, and add a comment below explaining why the
      zero-termination is one less than the bound.  markus@ ok
+   - markus@cvs.openbsd.org 2003/07/10 14:42:28
+     [packet.c]
+     the 2^(blocksize*2) rekeying limit is too expensive for 3DES,
+     blowfish, etc, so enforce a 1GB limit for small blocksizes.
 
 20030708
  - (dtucker) [acconfig.h auth-passwd.c configure.ac session.c port-aix.[ch]]
@@ -686,4 +690,4 @@
  - Fix sshd BindAddress and -b options for systems using fake-getaddrinfo.
    Report from murple@murple.net, diagnosis from dtucker@zip.com.au
 
-$Id: ChangeLog,v 1.2854 2003/07/14 07:28:34 dtucker Exp $
+$Id: ChangeLog,v 1.2855 2003/07/14 07:31:06 dtucker Exp $
diff --git a/packet.c b/packet.c
index 022212074..4ef639fd6 100644
--- a/packet.c
+++ b/packet.c
@@ -37,7 +37,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: packet.c,v 1.108 2003/06/24 08:23:46 markus Exp $");
+RCSID("$OpenBSD: packet.c,v 1.109 2003/07/10 14:42:28 markus Exp $");
 
 #include "openbsd-compat/sys-queue.h"
 
@@ -635,7 +635,14 @@ set_newkeys(int mode)
 			buffer_compress_init_recv();
 		comp->enabled = 1;
 	}
-	*max_blocks = ((u_int64_t)1 << (enc->block_size*2));
+	/*
+	 * The 2^(blocksize*2) limit is too expensive for 3DES,
+	 * blowfish, etc, so enforce a 1GB limit for small blocksizes.
+	 */
+	if (enc->block_size >= 16)
+		*max_blocks = (u_int64_t)1 << (enc->block_size*2);
+	else
+		*max_blocks = ((u_int64_t)1 << 30) / enc->block_size;
 	if (rekey_limit)
 		*max_blocks = MIN(*max_blocks, rekey_limit / enc->block_size);
 }