diff --git a/core/decoder.sv b/core/decoder.sv
index 0ebf6b981..4961e9523 100644
--- a/core/decoder.sv
+++ b/core/decoder.sv
@@ -221,8 +221,9 @@ module decoder
                 default: begin
                   if (instr.instr[31:25] == 7'b1001) begin
                     // check privilege level, SFENCE.VMA can only be executed in M/S mode
+                    // only if S mode is supported
                     // otherwise decode an illegal instruction
-                    illegal_instr    = (((CVA6Cfg.RVS && priv_lvl_i == riscv::PRIV_LVL_S) || ((!CVA6Cfg.RVS && !CVA6Cfg.RVU) || priv_lvl_i == riscv::PRIV_LVL_M)) && instr.itype.rd == '0) ? 1'b0 : 1'b1;
+                    illegal_instr    = (CVA6Cfg.RVS && (priv_lvl_i inside {riscv::PRIV_LVL_M, riscv::PRIV_LVL_S}) && instr.itype.rd == '0) ? 1'b0 : 1'b1;
                     instruction_o.op = ariane_pkg::SFENCE_VMA;
                     // check TVM flag and intercept SFENCE.VMA call if necessary
                     if (CVA6Cfg.RVS && priv_lvl_i == riscv::PRIV_LVL_S && tvm_i)