diff --git a/src/arch/riscv/isa/decoder.isa b/src/arch/riscv/isa/decoder.isa
index 2f2d43f0cf..678e662251 100644
--- a/src/arch/riscv/isa/decoder.isa
+++ b/src/arch/riscv/isa/decoder.isa
@@ -3467,11 +3467,11 @@ decode QUADRANT default Unknown::unknown() {
                 }
                 format VectorIntVxsatFormat{
                     0x20: vsaddu_vi({{
-                        Vd_vu[i] = sat_addu<vu>(Vs2_vu[i], (vu)SIMM5,
+                        Vd_vu[i] = sat_addu<vu>(Vs2_vu[i], (vu)sext<5>(SIMM5),
                             vxsatptr);
                     }}, OPIVI, VectorIntegerArithOp);
                     0x21: vsadd_vi({{
-                        Vd_vu[i] = sat_add<vi>(Vs2_vu[i], (vu)SIMM5,
+                        Vd_vi[i] = sat_add<vi>(Vs2_vi[i], (vi)sext<5>(SIMM5),
                             vxsatptr);
                     }}, OPIVI, VectorIntegerArithOp);
                 }