diff --git a/osm_nbi/instance_topics.py b/osm_nbi/instance_topics.py
index 6922112..22580d1 100644
--- a/osm_nbi/instance_topics.py
+++ b/osm_nbi/instance_topics.py
@@ -14,6 +14,7 @@
 # limitations under the License.
 
 # import logging
+import json
 from uuid import uuid4
 from http import HTTPStatus
 from time import time
@@ -239,14 +240,16 @@
                             where_, k
                         )
                     )
-                if "." in k or "$" in k:
+                if "$" in k:
                     raise EngineException(
-                        "Invalid param at {}:{}. Keys must not contain dots or $".format(
+                        "Invalid param at {}:{}. Keys must not contain $ symbol".format(
                             where_, k
                         )
                     )
                 if isinstance(v, (dict, tuple, list)):
                     additional_params[k] = "!!yaml " + safe_dump(v)
+            if kdu_name:
+                additional_params = json.dumps(additional_params)
 
         if descriptor:
             for df in descriptor.get("df", []):
@@ -1987,6 +1990,10 @@
                         HTTPStatus.CONFLICT,
                     )
             self._check_ns_operation(session, nsr, operation, indata)
+            if (indata.get("primitive_params")):
+                indata["primitive_params"] = json.dumps(indata["primitive_params"])
+            elif (indata.get("additionalParamsForVnf")):
+                indata["additionalParamsForVnf"] = json.dumps(indata["additionalParamsForVnf"])
 
             if operation == "instantiate":
                 self._update_vnfrs_from_nsd(nsr)