diff --git a/src/wasm/function-body-decoder-impl.h b/src/wasm/function-body-decoder-impl.h
index c52a26a547..9cb7f84722 100644
--- a/src/wasm/function-body-decoder-impl.h
+++ b/src/wasm/function-body-decoder-impl.h
@@ -5128,27 +5128,29 @@ class WasmFullDecoder : public WasmDecoder<ValidationTag, decoding_mode> {
         // Temporary non-standard instruction, for performance experiments.
         if (!VALIDATE(this->enabled_.has_ref_cast_nop())) {
           this->DecodeError(
-              "Invalid opcode 0xfb48 (enable with "
+              "Invalid opcode 0xfb4c (enable with "
               "--experimental-wasm-ref-cast-nop)");
           return 0;
         }
-        IndexImmediate imm(this, this->pc_ + opcode_length, "type index",
-                           validate);
-        if (!this->ValidateType(this->pc_ + opcode_length, imm)) return 0;
+        HeapTypeImmediate imm(this->enabled_, this, this->pc_ + opcode_length,
+                              validate);
+        if (!this->Validate(this->pc_ + opcode_length, imm)) return 0;
         opcode_length += imm.length;
+        HeapType target_type = imm.type;
         Value obj = Peek(0);
-        if (!VALIDATE(IsSubtypeOf(obj.type, kWasmFuncRef, this->module_) ||
-                      IsSubtypeOf(obj.type, kWasmStructRef, this->module_) ||
-                      IsSubtypeOf(obj.type, kWasmArrayRef, this->module_) ||
+        if (!VALIDATE((obj.type.is_object_reference() &&
+                       IsSameTypeHierarchy(obj.type.heap_type(), target_type,
+                                           this->module_)) ||
                       obj.type.is_bottom())) {
-          PopTypeError(0, obj,
-                       "subtype of (ref null func), (ref null struct) or (ref "
-                       "null array)");
+          this->DecodeError(
+              obj.pc(),
+              "Invalid types for %s: %s of type %s has to "
+              "be in the same reference type hierarchy as (ref %s)",
+              WasmOpcodes::OpcodeName(opcode), SafeOpcodeNameAt(obj.pc()),
+              obj.type.name().c_str(), target_type.name().c_str());
           return 0;
         }
-        Value value = CreateValue(ValueType::RefMaybeNull(
-            imm.index,
-            obj.type.is_bottom() ? kNonNullable : obj.type.nullability()));
+        Value value = CreateValue(ValueType::Ref(target_type));
         CALL_INTERFACE_IF_OK_AND_REACHABLE(Forward, obj, &value);
         Drop(obj);
         Push(value);