diff --git a/src/openApi/v2/parser/getModel.ts b/src/openApi/v2/parser/getModel.ts
index 48798383..5c3c5ac8 100644
--- a/src/openApi/v2/parser/getModel.ts
+++ b/src/openApi/v2/parser/getModel.ts
@@ -22,7 +22,7 @@ export function getModel(openApi: OpenApi, definition: OpenApiSchema, isDefiniti
         isDefinition,
         isReadOnly: definition.readOnly === true,
         isNullable: definition['x-nullable'] === true,
-        isRequired: definition.default !== undefined,
+        isRequired: false,
         format: definition.format,
         maximum: definition.maximum,
         exclusiveMaximum: definition.exclusiveMaximum,
diff --git a/src/openApi/v2/parser/getModelProperties.ts b/src/openApi/v2/parser/getModelProperties.ts
index 8d17386d..e1dcf27e 100644
--- a/src/openApi/v2/parser/getModelProperties.ts
+++ b/src/openApi/v2/parser/getModelProperties.ts
@@ -15,7 +15,7 @@ export function getModelProperties(openApi: OpenApi, definition: OpenApiSchema,
     for (const propertyName in definition.properties) {
         if (definition.properties.hasOwnProperty(propertyName)) {
             const property = definition.properties[propertyName];
-            const propertyRequired = definition.required?.includes(propertyName) || property.default !== undefined;
+            const propertyRequired = !!definition.required?.includes(propertyName);
             if (property.$ref) {
                 const model = getType(property.$ref);
                 models.push({
diff --git a/src/openApi/v2/parser/sortByRequired.ts b/src/openApi/v2/parser/sortByRequired.ts
index 05eceb4a..62d380db 100644
--- a/src/openApi/v2/parser/sortByRequired.ts
+++ b/src/openApi/v2/parser/sortByRequired.ts
@@ -1,9 +1,23 @@
 import type { OperationParameter } from '../../../client/interfaces/OperationParameter';
 
 export function sortByRequired(a: OperationParameter, b: OperationParameter): number {
-    const aNeedsValue = a.isRequired && a.default === undefined;
-    const bNeedsValue = b.isRequired && b.default === undefined;
-    if (aNeedsValue && !bNeedsValue) return -1;
-    if (!aNeedsValue && bNeedsValue) return 1;
+    const aIsRequiredWithoutDefaultValue = a.isRequired && a.default === undefined;
+    const bIsRequiredWithoutDefaultValue = b.isRequired && b.default === undefined;
+    const aIsRequiredWithDefaultValue = a.isRequired && a.default !== undefined;
+    const bIsRequiredWithDefaultValue = b.isRequired && b.default !== undefined;
+    const aIsOptionalWithDefaultValue = !a.isRequired && a.default !== undefined;
+    const bIsOptionalWithDefaultValue = !b.isRequired && b.default !== undefined;
+    const aIsOptionalWithoutDefaultValue = !a.isRequired && a.default === undefined;
+    const bIsOptionalWithoutDefaultValue = !b.isRequired && b.default === undefined;
+
+    if (aIsRequiredWithoutDefaultValue && !bIsRequiredWithoutDefaultValue) return -1;
+    if (bIsRequiredWithoutDefaultValue && !aIsRequiredWithoutDefaultValue) return 1;
+    if (aIsRequiredWithDefaultValue && !bIsRequiredWithDefaultValue) return -1;
+    if (bIsRequiredWithDefaultValue && !aIsRequiredWithDefaultValue) return 1;
+    if (aIsOptionalWithDefaultValue && !bIsOptionalWithDefaultValue) return -1;
+    if (bIsOptionalWithDefaultValue && !aIsOptionalWithDefaultValue) return 1;
+    if (aIsOptionalWithoutDefaultValue && !bIsOptionalWithoutDefaultValue) return -1;
+    if (bIsOptionalWithoutDefaultValue && !aIsOptionalWithoutDefaultValue) return 1;
+
     return 0;
 }
diff --git a/src/openApi/v3/parser/getModel.ts b/src/openApi/v3/parser/getModel.ts
index 29007ae8..cac718ce 100644
--- a/src/openApi/v3/parser/getModel.ts
+++ b/src/openApi/v3/parser/getModel.ts
@@ -23,7 +23,7 @@ export function getModel(openApi: OpenApi, definition: OpenApiSchema, isDefiniti
         isDefinition,
         isReadOnly: definition.readOnly === true,
         isNullable: definition.nullable === true,
-        isRequired: definition.default !== undefined,
+        isRequired: false,
         format: definition.format,
         maximum: definition.maximum,
         exclusiveMaximum: definition.exclusiveMaximum,
diff --git a/src/openApi/v3/parser/getModelProperties.ts b/src/openApi/v3/parser/getModelProperties.ts
index ff22fe5a..1f1d80ce 100644
--- a/src/openApi/v3/parser/getModelProperties.ts
+++ b/src/openApi/v3/parser/getModelProperties.ts
@@ -15,7 +15,7 @@ export function getModelProperties(openApi: OpenApi, definition: OpenApiSchema,
     for (const propertyName in definition.properties) {
         if (definition.properties.hasOwnProperty(propertyName)) {
             const property = definition.properties[propertyName];
-            const propertyRequired = definition.required?.includes(propertyName) || property.default !== undefined;
+            const propertyRequired = !!definition.required?.includes(propertyName);
             if (property.$ref) {
                 const model = getType(property.$ref);
                 models.push({
diff --git a/src/openApi/v3/parser/sortByRequired.ts b/src/openApi/v3/parser/sortByRequired.ts
index 05eceb4a..62d380db 100644
--- a/src/openApi/v3/parser/sortByRequired.ts
+++ b/src/openApi/v3/parser/sortByRequired.ts
@@ -1,9 +1,23 @@
 import type { OperationParameter } from '../../../client/interfaces/OperationParameter';
 
 export function sortByRequired(a: OperationParameter, b: OperationParameter): number {
-    const aNeedsValue = a.isRequired && a.default === undefined;
-    const bNeedsValue = b.isRequired && b.default === undefined;
-    if (aNeedsValue && !bNeedsValue) return -1;
-    if (!aNeedsValue && bNeedsValue) return 1;
+    const aIsRequiredWithoutDefaultValue = a.isRequired && a.default === undefined;
+    const bIsRequiredWithoutDefaultValue = b.isRequired && b.default === undefined;
+    const aIsRequiredWithDefaultValue = a.isRequired && a.default !== undefined;
+    const bIsRequiredWithDefaultValue = b.isRequired && b.default !== undefined;
+    const aIsOptionalWithDefaultValue = !a.isRequired && a.default !== undefined;
+    const bIsOptionalWithDefaultValue = !b.isRequired && b.default !== undefined;
+    const aIsOptionalWithoutDefaultValue = !a.isRequired && a.default === undefined;
+    const bIsOptionalWithoutDefaultValue = !b.isRequired && b.default === undefined;
+
+    if (aIsRequiredWithoutDefaultValue && !bIsRequiredWithoutDefaultValue) return -1;
+    if (bIsRequiredWithoutDefaultValue && !aIsRequiredWithoutDefaultValue) return 1;
+    if (aIsRequiredWithDefaultValue && !bIsRequiredWithDefaultValue) return -1;
+    if (bIsRequiredWithDefaultValue && !aIsRequiredWithDefaultValue) return 1;
+    if (aIsOptionalWithDefaultValue && !bIsOptionalWithDefaultValue) return -1;
+    if (bIsOptionalWithDefaultValue && !aIsOptionalWithDefaultValue) return 1;
+    if (aIsOptionalWithoutDefaultValue && !bIsOptionalWithoutDefaultValue) return -1;
+    if (bIsOptionalWithoutDefaultValue && !aIsOptionalWithoutDefaultValue) return 1;
+
     return 0;
 }
diff --git a/test/__snapshots__/index.spec.js.snap b/test/__snapshots__/index.spec.js.snap
index 74637bbd..2bcaf7ba 100644
--- a/test/__snapshots__/index.spec.js.snap
+++ b/test/__snapshots__/index.spec.js.snap
@@ -1927,31 +1927,31 @@ export class DefaultsService {
 
     /**
      * @param parameterStringWithNoDefault This is a string with no default
+     * @param parameterStringWithDefault This is a string with default
+     * @param parameterStringWithEmptyDefault This is a string with empty default
      * @param parameterOptionalStringWithDefault This is a optional string with default
      * @param parameterOptionalStringWithEmptyDefault This is a optional string with empty default
      * @param parameterOptionalStringWithNoDefault This is a optional string with no default
-     * @param parameterStringWithDefault This is a string with default
-     * @param parameterStringWithEmptyDefault This is a string with empty default
      * @throws ApiError
      */
     public static async callToTestOrderOfParams(
         parameterStringWithNoDefault: string,
+        parameterStringWithDefault: string = 'Hello World!',
+        parameterStringWithEmptyDefault: string = '',
         parameterOptionalStringWithDefault: string = 'Hello World!',
         parameterOptionalStringWithEmptyDefault: string = '',
         parameterOptionalStringWithNoDefault?: string,
-        parameterStringWithDefault: string = 'Hello World!',
-        parameterStringWithEmptyDefault: string = '',
     ): Promise<void> {
         const result = await __request({
             method: 'PUT',
             path: \`/api/v\${OpenAPI.VERSION}/defaults\`,
             query: {
                 'parameterStringWithNoDefault': parameterStringWithNoDefault,
+                'parameterStringWithDefault': parameterStringWithDefault,
+                'parameterStringWithEmptyDefault': parameterStringWithEmptyDefault,
                 'parameterOptionalStringWithDefault': parameterOptionalStringWithDefault,
                 'parameterOptionalStringWithEmptyDefault': parameterOptionalStringWithEmptyDefault,
                 'parameterOptionalStringWithNoDefault': parameterOptionalStringWithNoDefault,
-                'parameterStringWithDefault': parameterStringWithDefault,
-                'parameterStringWithEmptyDefault': parameterStringWithEmptyDefault,
             },
         });
         return result.body;
@@ -4493,7 +4493,7 @@ export class ComplexService {
         requestBody?: {
             readonly key: string | null,
             name: string | null,
-            enabled: boolean,
+            enabled?: boolean,
             readonly type: 'Monkey' | 'Horse' | 'Bird',
             listOfModels?: Array<ModelWithString> | null,
             listOfStrings?: Array<string> | null,
@@ -4590,31 +4590,31 @@ export class DefaultsService {
 
     /**
      * @param parameterStringWithNoDefault This is a string with no default
+     * @param parameterStringWithDefault This is a string with default
+     * @param parameterStringWithEmptyDefault This is a string with empty default
      * @param parameterOptionalStringWithDefault This is a optional string with default
      * @param parameterOptionalStringWithEmptyDefault This is a optional string with empty default
      * @param parameterOptionalStringWithNoDefault This is a optional string with no default
-     * @param parameterStringWithDefault This is a string with default
-     * @param parameterStringWithEmptyDefault This is a string with empty default
      * @throws ApiError
      */
     public static async callToTestOrderOfParams(
         parameterStringWithNoDefault: string,
+        parameterStringWithDefault: string = 'Hello World!',
+        parameterStringWithEmptyDefault: string = '',
         parameterOptionalStringWithDefault: string = 'Hello World!',
         parameterOptionalStringWithEmptyDefault: string = '',
         parameterOptionalStringWithNoDefault?: string,
-        parameterStringWithDefault: string = 'Hello World!',
-        parameterStringWithEmptyDefault: string = '',
     ): Promise<void> {
         const result = await __request({
             method: 'PUT',
             path: \`/api/v\${OpenAPI.VERSION}/defaults\`,
             query: {
                 'parameterStringWithNoDefault': parameterStringWithNoDefault,
+                'parameterStringWithDefault': parameterStringWithDefault,
+                'parameterStringWithEmptyDefault': parameterStringWithEmptyDefault,
                 'parameterOptionalStringWithDefault': parameterOptionalStringWithDefault,
                 'parameterOptionalStringWithEmptyDefault': parameterOptionalStringWithEmptyDefault,
                 'parameterOptionalStringWithNoDefault': parameterOptionalStringWithNoDefault,
-                'parameterStringWithDefault': parameterStringWithDefault,
-                'parameterStringWithEmptyDefault': parameterStringWithEmptyDefault,
             },
         });
         return result.body;