diff --git a/ipemu/src/TestBench.scala b/ipemu/src/TestBench.scala
index 7cebddac0..5a5e37ec3 100644
--- a/ipemu/src/TestBench.scala
+++ b/ipemu/src/TestBench.scala
@@ -115,10 +115,11 @@ class TestBench(generator: SerializableModuleGenerator[T1, T1Parameter]) extends
     outstanding := outstanding + (doIssue && (issue.meta === 1.U)) - dut.response.valid
     fence := Mux(doIssue, issue.meta === 2.U, fence && !dut.response.valid && !(outstanding === 0.U))
 
-    issue := RawClockedNonVoidFunctionCall("issue_vector_instruction", new Issue)(
+    // RawClockedNonVoidFunctionCall result is initialized to X, hack it to zero
+    issue := Mux(RegNext(true.B, false.B), RawClockedNonVoidFunctionCall("issue_vector_instruction", new Issue)(
       clock,
       doIssue,
-    )
+    ), 0.U.asTypeOf(new Issue))
     dut.request.bits.instruction := issue.instruction
     dut.request.bits.src1Data := issue.src1Data
     dut.request.bits.src2Data := issue.src2Data