diff --git a/himbaechel/uarch/ng-ultra/pack.cc b/himbaechel/uarch/ng-ultra/pack.cc
index ba9cd588..66f38c45 100644
--- a/himbaechel/uarch/ng-ultra/pack.cc
+++ b/himbaechel/uarch/ng-ultra/pack.cc
@@ -416,6 +416,7 @@ void NgUltraPacker::pack_iobs(void)
             new_type = id_IOTP;
             if (ci.type==id_NX_IOB_O) new_type = id_OTP;
             if (ci.type==id_NX_IOB_I) new_type = id_ITP;
+            log_error("JSON import currently does not support IOs with termination input.\n");
         } else {
             if (ci.type==id_NX_IOB_O) new_type = id_OP;
             if (ci.type==id_NX_IOB_I) new_type = id_IP;