diff --git a/src/main/java/com/twilio/rest/accounts/v1/BulkConsentsCreator.java b/src/main/java/com/twilio/rest/accounts/v1/BulkConsentsCreator.java
index ad5acc7da5..b472c75f67 100644
--- a/src/main/java/com/twilio/rest/accounts/v1/BulkConsentsCreator.java
+++ b/src/main/java/com/twilio/rest/accounts/v1/BulkConsentsCreator.java
@@ -15,6 +15,7 @@
 package com.twilio.rest.accounts.v1;
 
 import com.twilio.base.Creator;
+import com.twilio.converter.Converter;
 import com.twilio.constant.EnumConstants;
 import com.twilio.converter.Promoter;
 import com.twilio.exception.ApiConnectionException;
@@ -86,7 +87,7 @@ public BulkConsents create(final TwilioRestClient client) {
     private void addPostParams(final Request request) {
         if (items != null) {
             for (Object prop : items) {
-                request.addPostParam("Items", prop.toString());
+                request.addPostParam("Items", Converter.objectToJson(prop));
             }
         }
     }
diff --git a/src/main/java/com/twilio/rest/accounts/v1/BulkContactsCreator.java b/src/main/java/com/twilio/rest/accounts/v1/BulkContactsCreator.java
index 2939c5c60d..abbd29d480 100644
--- a/src/main/java/com/twilio/rest/accounts/v1/BulkContactsCreator.java
+++ b/src/main/java/com/twilio/rest/accounts/v1/BulkContactsCreator.java
@@ -16,6 +16,7 @@
 
 import com.twilio.base.Creator;
 import com.twilio.constant.EnumConstants;
+import com.twilio.converter.Converter;
 import com.twilio.converter.Promoter;
 import com.twilio.exception.ApiConnectionException;
 import com.twilio.exception.ApiException;
@@ -86,7 +87,7 @@ public BulkContacts create(final TwilioRestClient client) {
     private void addPostParams(final Request request) {
         if (items != null) {
             for (Object prop : items) {
-                request.addPostParam("Items", prop.toString());
+                request.addPostParam("Items", Converter.objectToJson(prop));
             }
         }
     }
diff --git a/src/main/java/com/twilio/rest/events/v1/SubscriptionCreator.java b/src/main/java/com/twilio/rest/events/v1/SubscriptionCreator.java
index e82e798efa..fd9b3c97e5 100644
--- a/src/main/java/com/twilio/rest/events/v1/SubscriptionCreator.java
+++ b/src/main/java/com/twilio/rest/events/v1/SubscriptionCreator.java
@@ -15,6 +15,7 @@
 package com.twilio.rest.events.v1;
 
 import com.twilio.base.Creator;
+import com.twilio.converter.Converter;
 import com.twilio.constant.EnumConstants;
 import com.twilio.converter.Promoter;
 import com.twilio.exception.ApiConnectionException;
@@ -116,7 +117,7 @@ private void addPostParams(final Request request) {
         }
         if (types != null) {
             for (Object prop : types) {
-                request.addPostParam("Types", prop.toString());
+                request.addPostParam("Types", Converter.objectToJson(prop));
             }
         }
     }
diff --git a/src/main/java/com/twilio/rest/flexapi/v1/PluginConfigurationCreator.java b/src/main/java/com/twilio/rest/flexapi/v1/PluginConfigurationCreator.java
index d55ca90f44..19dbfd4fee 100644
--- a/src/main/java/com/twilio/rest/flexapi/v1/PluginConfigurationCreator.java
+++ b/src/main/java/com/twilio/rest/flexapi/v1/PluginConfigurationCreator.java
@@ -16,6 +16,7 @@
 
 import com.twilio.base.Creator;
 import com.twilio.constant.EnumConstants;
+import com.twilio.converter.Converter;
 import com.twilio.converter.Promoter;
 import com.twilio.exception.ApiConnectionException;
 import com.twilio.exception.ApiException;
@@ -110,7 +111,7 @@ private void addPostParams(final Request request) {
         }
         if (plugins != null) {
             for (Object prop : plugins) {
-                request.addPostParam("Plugins", prop.toString());
+                request.addPostParam("Plugins", Converter.objectToJson(prop));
             }
         }
         if (description != null) {
diff --git a/src/main/java/com/twilio/rest/proxy/v1/service/SessionCreator.java b/src/main/java/com/twilio/rest/proxy/v1/service/SessionCreator.java
index 7cabf721a5..8a936a5902 100644
--- a/src/main/java/com/twilio/rest/proxy/v1/service/SessionCreator.java
+++ b/src/main/java/com/twilio/rest/proxy/v1/service/SessionCreator.java
@@ -15,6 +15,7 @@
 package com.twilio.rest.proxy.v1.service;
 
 import com.twilio.base.Creator;
+import com.twilio.converter.Converter;
 import com.twilio.constant.EnumConstants;
 import com.twilio.converter.Promoter;
 import com.twilio.exception.ApiConnectionException;
@@ -137,7 +138,10 @@ private void addPostParams(final Request request) {
         }
         if (participants != null) {
             for (Object prop : participants) {
-                request.addPostParam("Participants", prop.toString());
+                request.addPostParam(
+                    "Participants",
+                    Converter.objectToJson(prop)
+                );
             }
         }
     }
diff --git a/src/main/java/com/twilio/rest/verify/v2/service/entity/ChallengeCreator.java b/src/main/java/com/twilio/rest/verify/v2/service/entity/ChallengeCreator.java
index 7db4865e5c..366f518740 100644
--- a/src/main/java/com/twilio/rest/verify/v2/service/entity/ChallengeCreator.java
+++ b/src/main/java/com/twilio/rest/verify/v2/service/entity/ChallengeCreator.java
@@ -149,7 +149,10 @@ private void addPostParams(final Request request) {
         }
         if (detailsFields != null) {
             for (Object prop : detailsFields) {
-                request.addPostParam("Details.Fields", prop.toString());
+                request.addPostParam(
+                    "Details.Fields",
+                    Converter.objectToJson(prop)
+                );
             }
         }
         if (hiddenDetails != null) {