diff --git a/nexus/pack.cc b/nexus/pack.cc
index b02d25c6..616da530 100644
--- a/nexus/pack.cc
+++ b/nexus/pack.cc
@@ -1232,10 +1232,12 @@ struct NexusPacker
         dict<IdString, XFormRule> base_iodelay_rules;
         base_iodelay_rules[id_DELAYB].new_type = id_IOLOGIC;
 
-        base_iodelay_rules[id_DELAYB].param_xform[id_DEL_VALUE] = ctx->id("DELAY.DEL_VALUE");
-        base_iodelay_rules[id_DELAYB].param_xform[id_COARSE_DELAY] = ctx->id("DELAY.COARSE_DELAY");
-
-        base_iodelay_rules[id_DELAYA] = base_iodelay_rules[id_DELAYB];
+        XFormRule delay_rule;
+        delay_rule.param_xform[id_DEL_VALUE] = ctx->id("DELAY.DEL_VALUE");
+        delay_rule.param_xform[id_COARSE_DELAY] = ctx->id("DELAY.COARSE_DELAY");
+        
+        base_iodelay_rules[id_DELAYB] = delay_rule;
+        base_iodelay_rules[id_DELAYA] = delay_rule;
 
         base_iodelay_rules[id_DELAYA].param_xform[id_COARSE_DELAY_MODE] = ctx->id("DELAY.COARSE_DELAY_MODE");
         base_iodelay_rules[id_DELAYA].param_xform[id_EDGE_MONITOR] = ctx->id("DELAY.EDGE_MONITOR");