diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PowerShellClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PowerShellClientCodegen.java
index 7c7ba4ba73f1..01f486dcdae8 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PowerShellClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PowerShellClientCodegen.java
@@ -29,6 +29,7 @@
 import org.openapitools.codegen.DefaultCodegen;
 import org.openapitools.codegen.SupportingFile;
 import org.openapitools.codegen.utils.ModelUtils;
+import org.openapitools.codegen.utils.ProcessUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -425,6 +426,16 @@ public Map<String, Object> postProcessOperationsWithModels(Map<String, Object> o
                 index++;
             }
         }
+
+        return objs;
+    }
+
+    @Override
+    public Map<String, Object> postProcessModels(Map<String, Object> objs) {
+        List<Object> models = (List<Object>) objs.get("models");
+        // add x-index to properties
+        ProcessUtils.addIndexToProperties(models);
         return objs;
     }
+
 }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ProcessUtils.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ProcessUtils.java
new file mode 100644
index 000000000000..c3943d67c9d0
--- /dev/null
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ProcessUtils.java
@@ -0,0 +1,37 @@
+package org.openapitools.codegen.utils;
+
+import org.openapitools.codegen.CodegenModel;
+import org.openapitools.codegen.CodegenProperty;
+
+import java.util.List;
+import java.util.Map;
+
+public class ProcessUtils {
+
+    /**
+     * Add x-index extension to the model's properties
+     *
+     * @param models  List of models
+     */
+    public static void addIndexToProperties(List<Object> models) {
+        for (Object _mo : models) {
+            Map<String, Object> mo = (Map<String, Object>) _mo;
+            CodegenModel cm = (CodegenModel) mo.get("model");
+
+            int i = 0;
+            for (CodegenProperty var : cm.vars) {
+                var.vendorExtensions.put("x-index", i);
+                i++;
+            }
+
+            int j = 0;
+            for (CodegenProperty var : cm.allVars) {
+                var.vendorExtensions.put("x-index", j);
+                j++;
+            }
+
+        }
+
+    }
+
+}
diff --git a/modules/openapi-generator/src/main/resources/powershell/model.mustache b/modules/openapi-generator/src/main/resources/powershell/model.mustache
index 8d74516b1214..8c2452cd0273 100644
--- a/modules/openapi-generator/src/main/resources/powershell/model.mustache
+++ b/modules/openapi-generator/src/main/resources/powershell/model.mustache
@@ -4,7 +4,7 @@ function New-{{{classname}}} {
     [CmdletBinding()]
     Param (
 {{#vars}}
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true{{#required}}, Mandatory = $true{{/required}})]
+        [Parameter(Position = {{vendorExtensions.x-index}}, ValueFromPipelineByPropertyName = $true{{#required}}, Mandatory = $true{{/required}})]
         [{{#isString}}{{{dataType}}}{{/isString}}{{^isString}}{{^required}}System.Nullable[{{/required}}{{dataType}}{{^required}}]{{/required}}{{/isString}}]
         {{=<% %>=}}
         ${<%name%>}<%^-last%>,<%/-last%>
diff --git a/samples/client/petstore/powershell/.openapi-generator/VERSION b/samples/client/petstore/powershell/.openapi-generator/VERSION
index 096bf47efe31..afa636560641 100644
--- a/samples/client/petstore/powershell/.openapi-generator/VERSION
+++ b/samples/client/petstore/powershell/.openapi-generator/VERSION
@@ -1 +1 @@
-3.0.0-SNAPSHOT
\ No newline at end of file
+4.0.0-SNAPSHOT
\ No newline at end of file
diff --git a/samples/client/petstore/powershell/src/Org.OpenAPITools/API/PetApi.ps1 b/samples/client/petstore/powershell/src/Org.OpenAPITools/API/PetApi.ps1
index b3f359df82ae..9eb13d258475 100644
--- a/samples/client/petstore/powershell/src/Org.OpenAPITools/API/PetApi.ps1
+++ b/samples/client/petstore/powershell/src/Org.OpenAPITools/API/PetApi.ps1
@@ -3,7 +3,7 @@ function Invoke-PetApiAddPet {
     Param (
         [Parameter(Position = 0, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true, Mandatory = $true)]
         [Org.OpenAPITools.Model.Pet]
-        ${pet}
+        ${body}
     )
 
     Process {
@@ -11,7 +11,7 @@ function Invoke-PetApiAddPet {
         $PSBoundParameters | Out-DebugParameter | Write-Debug
 
         $Script:PetApi.AddPet(
-            ${pet}
+            ${body}
         )
     }
 }
@@ -97,7 +97,7 @@ function Invoke-PetApiUpdatePet {
     Param (
         [Parameter(Position = 0, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true, Mandatory = $true)]
         [Org.OpenAPITools.Model.Pet]
-        ${pet}
+        ${body}
     )
 
     Process {
@@ -105,7 +105,7 @@ function Invoke-PetApiUpdatePet {
         $PSBoundParameters | Out-DebugParameter | Write-Debug
 
         $Script:PetApi.UpdatePet(
-            ${pet}
+            ${body}
         )
     }
 }
diff --git a/samples/client/petstore/powershell/src/Org.OpenAPITools/API/StoreApi.ps1 b/samples/client/petstore/powershell/src/Org.OpenAPITools/API/StoreApi.ps1
index cfd4cdc3b454..679176f56a24 100644
--- a/samples/client/petstore/powershell/src/Org.OpenAPITools/API/StoreApi.ps1
+++ b/samples/client/petstore/powershell/src/Org.OpenAPITools/API/StoreApi.ps1
@@ -53,7 +53,7 @@ function Invoke-StoreApiPlaceOrder {
     Param (
         [Parameter(Position = 0, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true, Mandatory = $true)]
         [Org.OpenAPITools.Model.Order]
-        ${order}
+        ${body}
     )
 
     Process {
@@ -61,7 +61,7 @@ function Invoke-StoreApiPlaceOrder {
         $PSBoundParameters | Out-DebugParameter | Write-Debug
 
         $Script:StoreApi.PlaceOrder(
-            ${order}
+            ${body}
         )
     }
 }
diff --git a/samples/client/petstore/powershell/src/Org.OpenAPITools/API/UserApi.ps1 b/samples/client/petstore/powershell/src/Org.OpenAPITools/API/UserApi.ps1
index d716a6203af2..d8eea661dcc2 100644
--- a/samples/client/petstore/powershell/src/Org.OpenAPITools/API/UserApi.ps1
+++ b/samples/client/petstore/powershell/src/Org.OpenAPITools/API/UserApi.ps1
@@ -3,7 +3,7 @@ function Invoke-UserApiCreateUser {
     Param (
         [Parameter(Position = 0, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true, Mandatory = $true)]
         [Org.OpenAPITools.Model.User]
-        ${user}
+        ${body}
     )
 
     Process {
@@ -11,7 +11,7 @@ function Invoke-UserApiCreateUser {
         $PSBoundParameters | Out-DebugParameter | Write-Debug
 
         $Script:UserApi.CreateUser(
-            ${user}
+            ${body}
         )
     }
 }
@@ -21,7 +21,7 @@ function Invoke-UserApiCreateUsersWithArrayInput {
     Param (
         [Parameter(Position = 0, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true, Mandatory = $true)]
         [Org.OpenAPITools.Model.User[]]
-        ${user}
+        ${body}
     )
 
     Process {
@@ -29,7 +29,7 @@ function Invoke-UserApiCreateUsersWithArrayInput {
         $PSBoundParameters | Out-DebugParameter | Write-Debug
 
         $Script:UserApi.CreateUsersWithArrayInput(
-            ${user}
+            ${body}
         )
     }
 }
@@ -39,7 +39,7 @@ function Invoke-UserApiCreateUsersWithListInput {
     Param (
         [Parameter(Position = 0, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true, Mandatory = $true)]
         [Org.OpenAPITools.Model.User[]]
-        ${user}
+        ${body}
     )
 
     Process {
@@ -47,7 +47,7 @@ function Invoke-UserApiCreateUsersWithListInput {
         $PSBoundParameters | Out-DebugParameter | Write-Debug
 
         $Script:UserApi.CreateUsersWithListInput(
-            ${user}
+            ${body}
         )
     }
 }
@@ -132,7 +132,7 @@ function Invoke-UserApiUpdateUser {
         ${username},
         [Parameter(Position = 1, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true, Mandatory = $true)]
         [Org.OpenAPITools.Model.User]
-        ${user}
+        ${body}
     )
 
     Process {
@@ -141,7 +141,7 @@ function Invoke-UserApiUpdateUser {
 
         $Script:UserApi.UpdateUser(
             ${username},
-            ${user}
+            ${body}
         )
     }
 }
diff --git a/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-ApiResponse.ps1 b/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-ApiResponse.ps1
index 8a06938adffb..deab379454fe 100644
--- a/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-ApiResponse.ps1
+++ b/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-ApiResponse.ps1
@@ -4,10 +4,10 @@ function New-ApiResponse {
         [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[Int32]]
         ${code},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 1, ValueFromPipelineByPropertyName = $true)]
         [String]
         ${type},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 2, ValueFromPipelineByPropertyName = $true)]
         [String]
         ${message}
     )
diff --git a/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Category.ps1 b/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Category.ps1
index 7edb296a6d98..b6b263f54cfd 100644
--- a/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Category.ps1
+++ b/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Category.ps1
@@ -4,7 +4,7 @@ function New-Category {
         [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[Int64]]
         ${id},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 1, ValueFromPipelineByPropertyName = $true)]
         [String]
         ${name}
     )
diff --git a/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Order.ps1 b/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Order.ps1
index 0249b9783501..3393772475f5 100644
--- a/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Order.ps1
+++ b/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Order.ps1
@@ -4,19 +4,19 @@ function New-Order {
         [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[Int64]]
         ${id},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 1, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[Int64]]
         ${petId},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 2, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[Int32]]
         ${quantity},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 3, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[System.DateTime]]
         ${shipDate},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 4, ValueFromPipelineByPropertyName = $true)]
         [String]
         ${status},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 5, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[Boolean]]
         ${complete}
     )
diff --git a/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Pet.ps1 b/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Pet.ps1
index 8dc289ea18cc..733267b0ac61 100644
--- a/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Pet.ps1
+++ b/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Pet.ps1
@@ -4,19 +4,19 @@ function New-Pet {
         [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[Int64]]
         ${id},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 1, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[Org.OpenAPITools.Model.Category]]
         ${category},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true, Mandatory = $true)]
+        [Parameter(Position = 2, ValueFromPipelineByPropertyName = $true, Mandatory = $true)]
         [String]
         ${name},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true, Mandatory = $true)]
+        [Parameter(Position = 3, ValueFromPipelineByPropertyName = $true, Mandatory = $true)]
         [String[]]
         ${photoUrls},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 4, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[Org.OpenAPITools.Model.Tag[]]]
         ${tags},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 5, ValueFromPipelineByPropertyName = $true)]
         [String]
         ${status}
     )
diff --git a/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Tag.ps1 b/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Tag.ps1
index d9e8ace5f968..e12f28e45330 100644
--- a/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Tag.ps1
+++ b/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-Tag.ps1
@@ -4,7 +4,7 @@ function New-Tag {
         [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[Int64]]
         ${id},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 1, ValueFromPipelineByPropertyName = $true)]
         [String]
         ${name}
     )
diff --git a/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-User.ps1 b/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-User.ps1
index c99036be250f..1b3ae9b1ca42 100644
--- a/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-User.ps1
+++ b/samples/client/petstore/powershell/src/Org.OpenAPITools/Model/New-User.ps1
@@ -4,25 +4,25 @@ function New-User {
         [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[Int64]]
         ${id},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 1, ValueFromPipelineByPropertyName = $true)]
         [String]
         ${username},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 2, ValueFromPipelineByPropertyName = $true)]
         [String]
         ${firstName},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 3, ValueFromPipelineByPropertyName = $true)]
         [String]
         ${lastName},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 4, ValueFromPipelineByPropertyName = $true)]
         [String]
         ${email},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 5, ValueFromPipelineByPropertyName = $true)]
         [String]
         ${password},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 6, ValueFromPipelineByPropertyName = $true)]
         [String]
         ${phone},
-        [Parameter(Position = 0, ValueFromPipelineByPropertyName = $true)]
+        [Parameter(Position = 7, ValueFromPipelineByPropertyName = $true)]
         [System.Nullable[Int32]]
         ${userStatus}
     )