diff --git a/lib/filterx/expr-assign.c b/lib/filterx/expr-assign.c
index c0bda7fd3..9c14c7190 100644
--- a/lib/filterx/expr-assign.c
+++ b/lib/filterx/expr-assign.c
@@ -22,6 +22,7 @@
  */
 #include "filterx/expr-assign.h"
 #include "filterx/object-primitive.h"
+#include "filterx/filterx-ref.h"
 #include "scratch-buffers.h"
 
 static FilterXObject *
@@ -29,7 +30,8 @@ _eval(FilterXExpr *s)
 {
   FilterXBinaryOp *self = (FilterXBinaryOp *) s;
 
-  FilterXObject *value = filterx_expr_eval(self->rhs);
+  FilterXObject *v = filterx_expr_eval(self->rhs);
+  FilterXObject *value = filterx_ref_new(v);
 
   if (!value)
     return NULL;
diff --git a/lib/filterx/expr-comparison.c b/lib/filterx/expr-comparison.c
index 9bb3484ea..b4ae480ac 100644
--- a/lib/filterx/expr-comparison.c
+++ b/lib/filterx/expr-comparison.c
@@ -24,6 +24,7 @@
 #include "filterx/expr-comparison.h"
 #include "filterx/object-datetime.h"
 #include "filterx/filterx-globals.h"
+#include "filterx/filterx-ref.h"
 #include "filterx/object-extractor.h"
 #include "filterx/object-primitive.h"
 #include "filterx/object-null.h"
@@ -140,6 +141,8 @@ _evaluate_as_num(FilterXObject *lhs, FilterXObject *rhs, gint operator)
 static gboolean
 _evaluate_type_aware(FilterXObject *lhs, FilterXObject *rhs, gint operator)
 {
+  lhs = filterx_ref_get_readonly_value(lhs);
+
   if (lhs->type == rhs->type &&
       (filterx_object_is_type(lhs, &FILTERX_TYPE_NAME(string)) ||
        filterx_object_is_type(lhs, &FILTERX_TYPE_NAME(bytes)) ||
diff --git a/lib/filterx/expr-literal-generator.c b/lib/filterx/expr-literal-generator.c
index b970be48f..91caf6566 100644
--- a/lib/filterx/expr-literal-generator.c
+++ b/lib/filterx/expr-literal-generator.c
@@ -23,6 +23,7 @@
 
 #include "filterx/expr-literal-generator.h"
 #include "filterx/object-primitive.h"
+#include "filterx/filterx-ref.h"
 
 struct FilterXLiteralGeneratorElem_
 {
@@ -83,7 +84,7 @@ _eval_elements(FilterXObject *fillable, GList *elements)
             return FALSE;
         }
 
-      FilterXObject *value = filterx_expr_eval(elem->value);
+      FilterXObject *value = filterx_ref_new(filterx_expr_eval(elem->value));
       if (!value)
         {
           filterx_object_unref(key);
diff --git a/lib/filterx/expr-plus-generator.c b/lib/filterx/expr-plus-generator.c
index 79c305a86..997f53b0d 100644
--- a/lib/filterx/expr-plus-generator.c
+++ b/lib/filterx/expr-plus-generator.c
@@ -24,6 +24,7 @@
 #include "expr-plus.h"
 #include "object-string.h"
 #include "filterx-eval.h"
+#include "filterx-ref.h"
 #include "scratch-buffers.h"
 #include "expr-generator.h"
 #include "object-list-interface.h"
@@ -39,6 +40,8 @@ typedef struct FilterXOperatorPlusGenerator
 static gboolean
 _generate_obj(FilterXOperatorPlusGenerator *self, FilterXObject *obj, FilterXObject *fillable)
 {
+  fillable = filterx_ref_get_writable_value(fillable);
+
   if (filterx_object_is_type(fillable, &FILTERX_TYPE_NAME(list)))
     return filterx_list_merge(fillable, obj);
 
diff --git a/lib/filterx/expr-regexp.c b/lib/filterx/expr-regexp.c
index 3a092ac7a..dcc81fb67 100644
--- a/lib/filterx/expr-regexp.c
+++ b/lib/filterx/expr-regexp.c
@@ -28,6 +28,7 @@
 #include "filterx/object-list-interface.h"
 #include "filterx/object-dict-interface.h"
 #include "filterx/expr-function.h"
+#include "filterx/filterx-ref.h"
 #include "compat/pcre.h"
 #include "scratch-buffers.h"
 
@@ -268,6 +269,8 @@ _store_matches_to_dict(pcre2_code_8 *pattern, const FilterXReMatchState *state,
 static gboolean
 _store_matches(pcre2_code_8 *pattern, const FilterXReMatchState *state, FilterXObject *fillable)
 {
+  fillable = filterx_ref_get_writable_value(fillable);
+
   if (filterx_object_is_type(fillable, &FILTERX_TYPE_NAME(list)))
     return _store_matches_to_list(pattern, state, fillable);
 
diff --git a/lib/filterx/expr-set-subscript.c b/lib/filterx/expr-set-subscript.c
index 9f6e7149e..c83d6dc93 100644
--- a/lib/filterx/expr-set-subscript.c
+++ b/lib/filterx/expr-set-subscript.c
@@ -23,6 +23,7 @@
 #include "filterx/expr-set-subscript.h"
 #include "filterx/object-primitive.h"
 #include "filterx/filterx-eval.h"
+#include "filterx/filterx-ref.h"
 #include "scratch-buffers.h"
 
 typedef struct _FilterXSetSubscript
@@ -62,7 +63,7 @@ _eval(FilterXExpr *s)
       goto exit;
     }
 
-  new_value = filterx_expr_eval(self->new_value);
+  new_value = filterx_ref_new(filterx_expr_eval(self->new_value));
   if (!new_value)
     goto exit;
 
diff --git a/lib/filterx/expr-setattr.c b/lib/filterx/expr-setattr.c
index c88a2d479..02989c7fe 100644
--- a/lib/filterx/expr-setattr.c
+++ b/lib/filterx/expr-setattr.c
@@ -24,6 +24,7 @@
 #include "filterx/object-primitive.h"
 #include "filterx/object-string.h"
 #include "filterx/filterx-eval.h"
+#include "filterx/filterx-ref.h"
 #include "scratch-buffers.h"
 
 typedef struct _FilterXSetAttr
@@ -50,7 +51,7 @@ _eval(FilterXExpr *s)
       goto exit;
     }
 
-  FilterXObject *new_value = filterx_expr_eval(self->new_value);
+  FilterXObject *new_value = filterx_ref_new(filterx_expr_eval(self->new_value));
   if (!new_value)
     goto exit;
 
diff --git a/lib/filterx/filterx-metrics-labels.c b/lib/filterx/filterx-metrics-labels.c
index 42b2a7d9c..65d6ffd09 100644
--- a/lib/filterx/filterx-metrics-labels.c
+++ b/lib/filterx/filterx-metrics-labels.c
@@ -24,6 +24,7 @@
 
 #include "filterx-metrics-labels.h"
 #include "filterx-eval.h"
+#include "filterx-ref.h"
 #include "expr-literal.h"
 #include "expr-literal-generator.h"
 #include "object-string.h"
@@ -226,14 +227,15 @@ _format_expr_to_cache(FilterXExpr *expr, DynMetricsStore *cache)
 
   gboolean success = FALSE;
 
-  if (!filterx_object_is_type(obj, &FILTERX_TYPE_NAME(dict)))
+  FilterXObject *inner_obj = filterx_ref_get_readonly_value(obj);
+  if (!filterx_object_is_type(inner_obj, &FILTERX_TYPE_NAME(dict)))
     {
       filterx_eval_push_error_info("failed to format metrics labels, labels must be a dict", expr,
-                                   g_strdup_printf("got %s instead", obj->type->name), TRUE);
+                                   g_strdup_printf("got %s instead", inner_obj->type->name), TRUE);
       goto exit;
     }
 
-  success = filterx_dict_iter(obj, _format_dict_elem_to_cache, cache);
+  success = filterx_dict_iter(inner_obj, _format_dict_elem_to_cache, cache);
   if (!success)
     goto exit;
 
diff --git a/lib/filterx/func-flatten.c b/lib/filterx/func-flatten.c
index e78954487..5c585c7c5 100644
--- a/lib/filterx/func-flatten.c
+++ b/lib/filterx/func-flatten.c
@@ -27,6 +27,7 @@
 #include "filterx/object-primitive.h"
 #include "filterx/object-string.h"
 #include "filterx/filterx-eval.h"
+#include "filterx/filterx-ref.h"
 #include "scratch-buffers.h"
 
 #define FILTERX_FUNC_FLATTEN_USAGE "Usage: flatten(dict, separator=\".\")"
@@ -70,7 +71,8 @@ _collect_modifications_from_elem(FilterXObject *key, FilterXObject *value, gpoin
   GString *key_buffer = ((gpointer *) user_data)[3];
   gboolean is_top_level = (gboolean) GPOINTER_TO_INT(((gpointer *) user_data)[4]);
 
-  if (filterx_object_is_type(value, &FILTERX_TYPE_NAME(dict)))
+  FilterXObject *inner_value = filterx_ref_get_readonly_value(value);
+  if (filterx_object_is_type(inner_value, &FILTERX_TYPE_NAME(dict)))
     {
       if (is_top_level)
         *top_level_dict_keys = g_list_prepend(*top_level_dict_keys, filterx_object_ref(key));
@@ -84,7 +86,7 @@ _collect_modifications_from_elem(FilterXObject *key, FilterXObject *value, gpoin
       g_string_append(key_buffer, self->separator);
 
       gpointer inner_user_data[] = { self, flattened_kvs, NULL, key_buffer, GINT_TO_POINTER(FALSE)};
-      gboolean result = filterx_dict_iter(value, _collect_modifications_from_elem, inner_user_data);
+      gboolean result = filterx_dict_iter(inner_value, _collect_modifications_from_elem, inner_user_data);
 
       g_string_truncate(key_buffer, orig_len);
       return result;
@@ -190,14 +192,15 @@ _eval(FilterXExpr *s)
 
   gboolean result = FALSE;
 
-  if (!filterx_object_is_type(dict, &FILTERX_TYPE_NAME(dict)))
+  FilterXObject *inner_dict = filterx_ref_get_writable_value(dict);
+  if (!filterx_object_is_type(inner_dict, &FILTERX_TYPE_NAME(dict)))
     {
       filterx_eval_push_error_info("object must be a dict", self->dict_expr,
-                                   g_strdup_printf("got %s instead", dict->type->name), TRUE);
+                                   g_strdup_printf("got %s instead", inner_dict->type->name), TRUE);
       goto exit;
     }
 
-  result = _flatten(self, dict);
+  result = _flatten(self, inner_dict);
 
 exit:
   filterx_object_unref(dict);
diff --git a/lib/filterx/func-unset-empties.c b/lib/filterx/func-unset-empties.c
index fff1affca..b9e544420 100644
--- a/lib/filterx/func-unset-empties.c
+++ b/lib/filterx/func-unset-empties.c
@@ -32,6 +32,7 @@
 #include "filterx/object-list-interface.h"
 #include "filterx/filterx-eval.h"
 #include "filterx/filterx-globals.h"
+#include "filterx/filterx-ref.h"
 #include "filterx/func-flags.h"
 #include "filterx/expr-literal-generator.h"
 #include "filterx/expr-literal.h"
@@ -104,6 +105,8 @@ static gboolean _should_unset_string(FilterXFunctionUnsetEmpties *self, FilterXO
 static gboolean
 _should_unset(FilterXFunctionUnsetEmpties *self, FilterXObject *obj)
 {
+  obj = filterx_ref_get_readonly_value(obj);
+
   if (check_flag(self->flags, FILTERX_FUNC_UNSET_EMPTIES_FLAG_REPLACE_NULL) &&
       filterx_object_is_type(obj, &FILTERX_TYPE_NAME(null)))
     return TRUE;
@@ -129,6 +132,8 @@ _add_key_to_unset_list_if_needed(FilterXObject *key, FilterXObject *value, gpoin
 
   if (check_flag(self->flags, FILTERX_FUNC_UNSET_EMPTIES_FLAG_RECURSIVE))
     {
+      value = filterx_ref_get_readonly_value(value);
+
       if (filterx_object_is_type(value, &FILTERX_TYPE_NAME(dict)) && !_process_dict(self, value))
         return FALSE;
       if (filterx_object_is_type(value, &FILTERX_TYPE_NAME(list)) && !_process_list(self, value))
@@ -189,14 +194,16 @@ _process_list(FilterXFunctionUnsetEmpties *self, FilterXObject *obj)
     {
       FilterXObject *elem = filterx_list_get_subscript(obj, i);
 
+      FilterXObject *inner_elem = filterx_ref_get_readonly_value(elem);
+
       if (check_flag(self->flags, FILTERX_FUNC_UNSET_EMPTIES_FLAG_RECURSIVE))
         {
-          if (filterx_object_is_type(elem, &FILTERX_TYPE_NAME(dict)) && !_process_dict(self, elem))
+          if (filterx_object_is_type(inner_elem, &FILTERX_TYPE_NAME(dict)) && !_process_dict(self, inner_elem))
             {
               filterx_object_unref(elem);
               return FALSE;
             }
-          if (filterx_object_is_type(elem, &FILTERX_TYPE_NAME(list)) && !_process_list(self, elem))
+          if (filterx_object_is_type(inner_elem, &FILTERX_TYPE_NAME(list)) && !_process_list(self, inner_elem))
             {
               filterx_object_unref(elem);
               return FALSE;
@@ -247,13 +254,15 @@ _eval(FilterXExpr *s)
       return NULL;
     }
 
-  if (filterx_object_is_type(obj, &FILTERX_TYPE_NAME(dict)))
-    return _eval_on_dict(self, obj);
+  FilterXObject *inner_obj = filterx_ref_get_writable_value(obj);
 
-  if (filterx_object_is_type(obj, &FILTERX_TYPE_NAME(list)))
-    return _eval_on_list(self, obj);
+  if (filterx_object_is_type(inner_obj, &FILTERX_TYPE_NAME(dict)))
+    return _eval_on_dict(self, inner_obj);
 
-  filterx_eval_push_error("Object must be dict or list. " FILTERX_FUNC_UNSET_EMPTIES_USAGE, s, obj);
+  if (filterx_object_is_type(inner_obj, &FILTERX_TYPE_NAME(list)))
+    return _eval_on_list(self, inner_obj);
+
+  filterx_eval_push_error("Object must be dict or list. " FILTERX_FUNC_UNSET_EMPTIES_USAGE, s, inner_obj);
   filterx_object_unref(obj);
   return NULL;
 }
@@ -350,6 +359,9 @@ _handle_target_object(FilterXFunctionUnsetEmpties *self, FilterXObject *target,
 {
   g_assert(target);
   guint64 len;
+
+  target = filterx_ref_get_readonly_value(target);
+
   if (filterx_object_is_type(target, &FILTERX_TYPE_NAME(null)))
     set_flag(&self->flags, FILTERX_FUNC_UNSET_EMPTIES_FLAG_REPLACE_NULL, TRUE);
   else if (filterx_object_is_type(target, &FILTERX_TYPE_NAME(list)))
diff --git a/lib/filterx/object-dict-interface.c b/lib/filterx/object-dict-interface.c
index aa185400f..5111c5b04 100644
--- a/lib/filterx/object-dict-interface.c
+++ b/lib/filterx/object-dict-interface.c
@@ -25,6 +25,7 @@
 #include "filterx/object-extractor.h"
 #include "filterx/object-string.h"
 #include "filterx/object-json.h"
+#include "filterx/filterx-ref.h"
 #include "str-utils.h"
 
 gboolean
@@ -53,6 +54,7 @@ filterx_dict_merge(FilterXObject *s, FilterXObject *other)
 {
   FilterXDict *self = (FilterXDict *) s;
 
+  other = filterx_ref_get_readonly_value(other);
   g_assert(filterx_object_is_type(other, &FILTERX_TYPE_NAME(dict)));
   return filterx_dict_iter(other, _add_elem_to_dict, self);
 }
@@ -214,6 +216,9 @@ filterx_dict_init_instance(FilterXDict *self, FilterXType *type)
 static FilterXObject *
 _add(FilterXObject *lhs_object, FilterXObject *rhs_object)
 {
+  lhs_object = filterx_ref_get_readonly_value(lhs_object);
+  rhs_object = filterx_ref_get_readonly_value(rhs_object);
+
   if (!filterx_object_is_type(lhs_object, &FILTERX_TYPE_NAME(dict)) ||
       !filterx_object_is_type(rhs_object, &FILTERX_TYPE_NAME(dict)))
     return NULL;
diff --git a/lib/filterx/object-json-array.c b/lib/filterx/object-json-array.c
index 49f5d5eff..5b12ab6f6 100644
--- a/lib/filterx/object-json-array.c
+++ b/lib/filterx/object-json-array.c
@@ -30,6 +30,7 @@
 #include "filterx/object-list-interface.h"
 #include "filterx/expr-function.h"
 #include "filterx/filterx-eval.h"
+#include "filterx/filterx-ref.h"
 
 #include "logmsg/type-hinting.h"
 #include "str-repr/encode.h"
@@ -328,6 +329,7 @@ filterx_json_array_new_from_args(FilterXExpr *s, GPtrArray *args)
 
   FilterXObject *arg = (FilterXObject *) g_ptr_array_index(args, 0);
 
+  arg = filterx_ref_get_readonly_value(arg);
   if (filterx_object_is_type(arg, &FILTERX_TYPE_NAME(json_array)))
     return filterx_object_ref(arg);
 
@@ -354,6 +356,8 @@ filterx_json_array_new_empty(void)
 const gchar *
 filterx_json_array_to_json_literal(FilterXObject *s)
 {
+  s = filterx_ref_get_readonly_value(s);
+
   FilterXJsonArray *self = (FilterXJsonArray *) s;
 
   if (!filterx_object_is_type(s, &FILTERX_TYPE_NAME(json_array)))
@@ -365,6 +369,8 @@ filterx_json_array_to_json_literal(FilterXObject *s)
 struct json_object *
 filterx_json_array_get_value(FilterXObject *s)
 {
+  s = filterx_ref_get_readonly_value(s);
+
   if (!filterx_object_is_type(s, &FILTERX_TYPE_NAME(json_array)))
     return NULL;
 
diff --git a/lib/filterx/object-json-object.c b/lib/filterx/object-json-object.c
index d8848d872..6455cce4b 100644
--- a/lib/filterx/object-json-object.c
+++ b/lib/filterx/object-json-object.c
@@ -27,6 +27,7 @@
 #include "filterx/object-primitive.h"
 #include "filterx/object-string.h"
 #include "filterx/filterx-weakrefs.h"
+#include "filterx/filterx-ref.h"
 #include "filterx/object-dict-interface.h"
 #include "syslog-ng.h"
 #include "str-utils.h"
@@ -293,6 +294,8 @@ filterx_json_object_new_empty(void)
 const gchar *
 filterx_json_object_to_json_literal(FilterXObject *s)
 {
+  s = filterx_ref_get_readonly_value(s);
+
   FilterXJsonObject *self = (FilterXJsonObject *) s;
 
   if (!filterx_object_is_type(s, &FILTERX_TYPE_NAME(json_object)))
@@ -304,6 +307,8 @@ filterx_json_object_to_json_literal(FilterXObject *s)
 struct json_object *
 filterx_json_object_get_value(FilterXObject *s)
 {
+  s = filterx_ref_get_readonly_value(s);
+
   if (!filterx_object_is_type(s, &FILTERX_TYPE_NAME(json_object)))
     return NULL;
 
diff --git a/lib/filterx/object-json.c b/lib/filterx/object-json.c
index 79aae3c73..a70a63cb1 100644
--- a/lib/filterx/object-json.c
+++ b/lib/filterx/object-json.c
@@ -29,6 +29,7 @@
 #include "filterx/object-list-interface.h"
 #include "filterx/object-message-value.h"
 #include "filterx/filterx-eval.h"
+#include "filterx/filterx-ref.h"
 
 #include "scanner/list-scanner/list-scanner.h"
 #include "str-repr/encode.h"
@@ -197,6 +198,8 @@ filterx_json_new_from_args(FilterXExpr *s, GPtrArray *args)
 
   FilterXObject *arg = (FilterXObject *) g_ptr_array_index(args, 0);
 
+  arg = filterx_ref_get_readonly_value(arg);
+
   if (filterx_object_is_type(arg, &FILTERX_TYPE_NAME(json_array)) ||
       filterx_object_is_type(arg, &FILTERX_TYPE_NAME(json_object)))
     return filterx_object_ref(arg);
@@ -252,6 +255,8 @@ filterx_json_new_from_object(struct json_object *jso)
 const gchar *
 filterx_json_to_json_literal(FilterXObject *s)
 {
+  s = filterx_ref_get_readonly_value(s);
+
   if (filterx_object_is_type(s, &FILTERX_TYPE_NAME(json_object)))
     return filterx_json_object_to_json_literal(s);
   if (filterx_object_is_type(s, &FILTERX_TYPE_NAME(json_array)))
diff --git a/lib/filterx/object-list-interface.c b/lib/filterx/object-list-interface.c
index 497ca0e99..679d3aaeb 100644
--- a/lib/filterx/object-list-interface.c
+++ b/lib/filterx/object-list-interface.c
@@ -24,6 +24,7 @@
 #include "filterx/object-list-interface.h"
 #include "filterx/object-primitive.h"
 #include "filterx/object-json.h"
+#include "filterx/filterx-ref.h"
 
 FilterXObject *
 filterx_list_get_subscript(FilterXObject *s, gint64 index)
@@ -64,6 +65,7 @@ filterx_list_unset_index(FilterXObject *s, gint64 index)
 gboolean
 filterx_list_merge(FilterXObject *s, FilterXObject *other)
 {
+  other = filterx_ref_get_readonly_value(other);
   g_assert(filterx_object_is_type(other, &FILTERX_TYPE_NAME(list)));
 
   guint64 len;
@@ -301,6 +303,9 @@ filterx_list_init_instance(FilterXList *self, FilterXType *type)
 static FilterXObject *
 _add(FilterXObject *lhs_object, FilterXObject *rhs_object)
 {
+  lhs_object = filterx_ref_get_readonly_value(lhs_object);
+  rhs_object = filterx_ref_get_readonly_value(rhs_object);
+
   if (!filterx_object_is_type(lhs_object, &FILTERX_TYPE_NAME(list)) ||
       !filterx_object_is_type(rhs_object, &FILTERX_TYPE_NAME(list)))
     return NULL;
diff --git a/modules/csvparser/filterx-func-format-csv.c b/modules/csvparser/filterx-func-format-csv.c
index 9d51f00a7..bf03f4666 100644
--- a/modules/csvparser/filterx-func-format-csv.c
+++ b/modules/csvparser/filterx-func-format-csv.c
@@ -27,6 +27,7 @@
 #include "filterx/object-dict-interface.h"
 #include "filterx/object-list-interface.h"
 #include "filterx/filterx-eval.h"
+#include "filterx/filterx-ref.h"
 
 #include "scratch-buffers.h"
 #include "utf8utils.h"
@@ -54,11 +55,12 @@ _append_to_buffer(FilterXObject *key, FilterXObject *value, gpointer user_data)
   if (!value)
     value = self->default_value;
 
-  if (filterx_object_is_type(value, &FILTERX_TYPE_NAME(dict)) ||
-      filterx_object_is_type(value, &FILTERX_TYPE_NAME(list)))
+  FilterXObject *inner_value = filterx_ref_get_readonly_value(value);
+  if (filterx_object_is_type(inner_value, &FILTERX_TYPE_NAME(dict)) ||
+      filterx_object_is_type(inner_value, &FILTERX_TYPE_NAME(list)))
     {
       msg_debug("FilterX: format_csv(): skipping object, type not supported",
-                evt_tag_str("type", value->type->name));
+                evt_tag_str("type", inner_value->type->name));
       return TRUE;
     }
 
@@ -113,7 +115,8 @@ _handle_dict_input(FilterXFunctionFormatCSV *self, FilterXObject *csv_data, GStr
   if (self->columns)
     {
       FilterXObject *cols = filterx_expr_eval(self->columns);
-      if (!cols || !filterx_object_is_type(cols, &FILTERX_TYPE_NAME(list)) || !filterx_object_len(cols, &size))
+      FilterXObject *inner_cols = filterx_ref_get_readonly_value(cols);
+      if (!inner_cols || !filterx_object_is_type(inner_cols, &FILTERX_TYPE_NAME(list)) || !filterx_object_len(cols, &size))
         {
           filterx_object_unref(cols);
           filterx_eval_push_error("Columns must represented as list. " FILTERX_FUNC_FORMAT_CSV_USAGE, &self->super.super, NULL);
@@ -148,9 +151,10 @@ _eval(FilterXExpr *s)
   gboolean success = FALSE;
   GString *formatted = scratch_buffers_alloc();
 
-  if (filterx_object_is_type(csv_data, &FILTERX_TYPE_NAME(list)))
+  FilterXObject *inner_csv_data = filterx_ref_get_readonly_value(csv_data);
+  if (filterx_object_is_type(inner_csv_data, &FILTERX_TYPE_NAME(list)))
     success = _handle_list_input(self, csv_data, formatted);
-  else if (filterx_object_is_type(csv_data, &FILTERX_TYPE_NAME(dict)))
+  else if (filterx_object_is_type(inner_csv_data, &FILTERX_TYPE_NAME(dict)))
     success = _handle_dict_input(self, csv_data, formatted);
   else
     filterx_eval_push_error("input must be a dict or list. " FILTERX_FUNC_FORMAT_CSV_USAGE, s, csv_data);