diff --git a/isa/isa.yaml b/isa/isa.yaml
index 69e7a94434a1fbeb7103416e9977b8c179135395..9d988d88fca8577b3866cf3456f3269df96f4d36 100644
--- a/isa/isa.yaml
+++ b/isa/isa.yaml
@@ -1071,7 +1071,7 @@ groups:
         properties: [method_id, literalarray_id, cp]
 
       - sig: ecma.classfieldadd v1:in:top, v2:in:top
-        acc: in:top
+        acc: inout:top
         prefix: ecma
         format: [pref_op_v1_8_v2_8]
         intrinsic_name: INTRINSIC_CLASS_FIELD_ADD
@@ -1090,7 +1090,7 @@ groups:
         intrinsic_name: INTRINSIC_CLASS_PRIVATE_METHOD_OR_ACCESSOR_ADD
 
       - sig: ecma.classprivatefieldadd string_id, v1:in:top, v2:in:top
-        acc: in:top
+        acc: inout:top
         prefix: ecma
         format: [pref_op_id_32_v1_8_v2_8]
         intrinsic_name: INTRINSIC_CLASS_PRIVATE_FIELD_ADD
@@ -1104,7 +1104,7 @@ groups:
         properties: [string_id, cp]
 
       - sig: ecma.classprivatefieldset string_id, v1:in:top, v2:in:top
-        acc: in:top
+        acc: inout:top
         prefix: ecma
         format: [pref_op_id_32_v1_8_v2_8]
         intrinsic_name: INTRINSIC_CLASS_PRIVATE_FIELD_SET