diff --git a/disas/riscv.c b/disas/riscv.c
index 3c17501120..74ad16eacd 100644
--- a/disas/riscv.c
+++ b/disas/riscv.c
@@ -600,7 +600,7 @@ static const rvc_constraint rvcc_mv[] = { rvc_imm_eq_zero, rvc_end };
 static const rvc_constraint rvcc_not[] = { rvc_imm_eq_n1, rvc_end };
 static const rvc_constraint rvcc_neg[] = { rvc_rs1_eq_x0, rvc_end };
 static const rvc_constraint rvcc_negw[] = { rvc_rs1_eq_x0, rvc_end };
-static const rvc_constraint rvcc_sext_w[] = { rvc_rs2_eq_x0, rvc_end };
+static const rvc_constraint rvcc_sext_w[] = { rvc_imm_eq_zero, rvc_end };
 static const rvc_constraint rvcc_seqz[] = { rvc_imm_eq_p1, rvc_end };
 static const rvc_constraint rvcc_snez[] = { rvc_rs1_eq_x0, rvc_end };
 static const rvc_constraint rvcc_sltz[] = { rvc_rs2_eq_x0, rvc_end };