diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index 312bf298b3..824e5e8aa8 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -1408,7 +1408,7 @@ static void decode_RV32_64C0(DisasContext *ctx)
     switch (funct3) {
     case 0:
         /* illegal */
-        if (ctx->opcode == 0) {
+        if (GET_C_ADDI4SPN_IMM(ctx->opcode) == 0) {
             gen_exception_illegal(ctx);
         } else {
             /* C.ADDI4SPN -> addi rd', x2, zimm[9:2]*/