diff --git a/difftest/difftest-def.h b/difftest/difftest-def.h
index 9906bed81..f08aa7df2 100644
--- a/difftest/difftest-def.h
+++ b/difftest/difftest-def.h
@@ -75,6 +75,7 @@
     ZICNTR_ISA_STRING \
     ZIHPM_ISA_STRING \
     SDTRIG_ISA_STRING \
+    "_zacas" \
     "_zba_zbb_zbc_zbs_zbkb_zbkc_zbkx" \
     "_zimop_zcmop_zcb" \
     "_zknd_zkne_zknh_zksed_zksh" \