diff --git a/insns/insn_lui.py b/insns/insn_lui.py
index 36da7bc..73aa428 100644
--- a/insns/insn_lui.py
+++ b/insns/insn_lui.py
@@ -14,4 +14,13 @@ class rvfi_insn_lui(rvfi_insn_U_type):
         m.d.comb += self.spec_rd_wdata.eq(Mux(self.spec_rd_addr, self.insn_imm, 0))
         m.d.comb += self.spec_pc_wdata.eq(self.rvfi_pc_rdata + 4)
 
+        # default assignments
+        m.d.comb += self.spec_rs1_addr.eq(0)
+        m.d.comb += self.spec_rs2_addr.eq(0)
+        m.d.comb += self.spec_trap.eq(~self.misa_ok)
+        m.d.comb += self.spec_mem_addr.eq(0)
+        m.d.comb += self.spec_mem_rmask.eq(0)
+        m.d.comb += self.spec_mem_wmask.eq(0)
+        m.d.comb += self.spec_mem_wdata.eq(0)
+
         return m