diff --git a/src/main/scala/vexriscv/VexRiscv.scala b/src/main/scala/vexriscv/VexRiscv.scala
index d3feda3..ed7e37e 100644
--- a/src/main/scala/vexriscv/VexRiscv.scala
+++ b/src/main/scala/vexriscv/VexRiscv.scala
@@ -136,10 +136,10 @@ class VexRiscv(val config : VexRiscvConfig) extends Component with Pipeline{
   plugins ++= config.plugins
 
   //regression usage
-  val lastStageInstruction = CombInit(stages.last.input(config.INSTRUCTION)).keep().addAttribute (Verilator.public)
-  val lastStagePc = CombInit(stages.last.input(config.PC)).keep().addAttribute(Verilator.public)
-  val lastStageIsValid = CombInit(stages.last.arbitration.isValid).keep().addAttribute(Verilator.public)
-  val lastStageIsFiring = CombInit(stages.last.arbitration.isFiring).keep().addAttribute(Verilator.public)
+  val lastStageInstruction = CombInit(stages.last.input(config.INSTRUCTION)).dontSimplifyIt().addAttribute (Verilator.public)
+  val lastStagePc = CombInit(stages.last.input(config.PC)).dontSimplifyIt().addAttribute(Verilator.public)
+  val lastStageIsValid = CombInit(stages.last.arbitration.isValid).dontSimplifyIt().addAttribute(Verilator.public)
+  val lastStageIsFiring = CombInit(stages.last.arbitration.isFiring).dontSimplifyIt().addAttribute(Verilator.public)
 
   //Verilator perf
   decode.arbitration.removeIt.noBackendCombMerge