diff --git a/tuning/data/data_handlers.py b/tuning/data/data_handlers.py
index e5a133f18..d033d01f4 100644
--- a/tuning/data/data_handlers.py
+++ b/tuning/data/data_handlers.py
@@ -17,6 +17,7 @@
 # Standard
 from enum import Enum
 from typing import Any, Dict, List, Union
+import json
 
 # import copy
 import logging
@@ -183,6 +184,7 @@ def __wrap_jinja_rendering_with_exception_handling(render_template: callable, **
 def apply_custom_jinja_template(
     element: Dict[str, str],
     formatted_text_column_name: str,
+    to_json: bool,
     template: str,
     **kwargs,
 ):
@@ -193,6 +195,7 @@ def apply_custom_jinja_template(
         formatted_text_column_name: Name of the dataset column where formatted
                                     text is to be saved. If doesn't exist a new
                                     column will be created.
+        to_json: whether to cast the output as a json
         template: Template to format data with. Features of Dataset
             should be referred to by {{key}}.
     Returns:
@@ -212,7 +215,16 @@ def render():
         env = SandboxedEnvironment(undefined=StrictUndefined)
         jinja_template = env.from_string(template)
         template_kwargs = {**tokenizer.special_tokens_map, **element}
-        return jinja_template.render(element=element, **template_kwargs)
+        res = jinja_template.render(element=element, **template_kwargs)
+        if to_json:
+            try:
+                # this can easily fail if the individual values in the template are not already json encoded
+                res = json.loads(res)
+            except json.decoder.JSONDecodeError as e:
+                raise RuntimeError(
+                    "Column data not in expected json format: %s" % (res)
+                ) from e
+        return res
 
     return {
         f"{formatted_text_column_name}": __wrap_jinja_rendering_with_exception_handling(