remove obsolete FIXME
diff --git a/lib/fusion.c b/lib/fusion.c
index 1bd40b9..eaa45e1 100644
--- a/lib/fusion.c
+++ b/lib/fusion.c
@@ -917,8 +917,7 @@
     ctx->super.do_encrypt = aead_do_encrypt;
     ctx->super.do_decrypt = aead_do_decrypt;
 
-    ctx->aesgcm =
-        ptls_fusion_aesgcm_new(key, key_size, 1500); /* FIXME use realloc with exponential back-off to support arbitrary size */
+    ctx->aesgcm = ptls_fusion_aesgcm_new(key, key_size, 1500 /* assume ordinary packet size */);
 
     return 0;
 }