diff --git a/src/apis/assistants.ts b/src/apis/assistants.ts
index ccbf610..80b8aca 100644
--- a/src/apis/assistants.ts
+++ b/src/apis/assistants.ts
@@ -2,7 +2,7 @@ import { ApiClientInterface } from "../_types/generalTypes";
 import { ApiResource } from "../apiResource";
 import { RequestOptions } from "../baseClient";
 import { OPEN_AI_API_KEY } from "../constants";
-import { finalResponse, overrideConfig } from "../utils";
+import { defaultHeadersBuilder, finalResponse, overrideConfig } from "../utils";
 import { createHeaders } from "./createHeaders";
 import OpenAI from "openai";
 
@@ -72,7 +72,7 @@ export class Assistants extends ApiResource {
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.assistants.create(body, opts).withResponse();
@@ -97,7 +97,7 @@ export class Assistants extends ApiResource {
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
          // @ts-ignore
         const result = await OAIclient.beta.assistants.list(query, opts).withResponse();
@@ -121,7 +121,7 @@ export class Assistants extends ApiResource {
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.assistants.retrieve(assistantId, opts).withResponse();
@@ -147,7 +147,7 @@ export class Assistants extends ApiResource {
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.assistants.update(assistantId, body, opts).withResponse();
@@ -171,7 +171,7 @@ export class Assistants extends ApiResource {
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.assistants.del(assistantId, opts).withResponse();
@@ -202,7 +202,7 @@ export class Files extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.assistants.files.create(assistantId, body, opts).withResponse();
@@ -228,7 +228,7 @@ export class Files extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
         // @ts-ignore
         const result = await OAIclient.beta.assistants.files.list(assistantId, query, opts).withResponse();
@@ -253,7 +253,7 @@ export class Files extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.assistants.files.retrieve(assistantId, fileId, opts).withResponse();
@@ -278,7 +278,7 @@ export class Files extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.assistants.files.del(assistantId, fileId, opts).withResponse();
diff --git a/src/apis/files.ts b/src/apis/files.ts
index 633a2d9..80ec7ad 100644
--- a/src/apis/files.ts
+++ b/src/apis/files.ts
@@ -2,7 +2,7 @@ import { ApiClientInterface } from "../_types/generalTypes";
 import { ApiResource } from "../apiResource";
 import { RequestOptions } from "../baseClient";
 import { OPEN_AI_API_KEY } from "../constants";
-import { finalResponse, overrideConfig } from "../utils";
+import { defaultHeadersBuilder, finalResponse, overrideConfig } from "../utils";
 import { createHeaders } from "./createHeaders";
 import OpenAI from "openai";
 
@@ -25,7 +25,7 @@ export class MainFiles extends ApiResource {
     const OAIclient = new OpenAI({
       apiKey: OPEN_AI_API_KEY,
       baseURL: this.client.baseURL,
-      defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+      defaultHeaders: defaultHeadersBuilder(this.client),
     });
     
     // @ts-ignore
@@ -51,7 +51,7 @@ export class MainFiles extends ApiResource {
     const OAIclient = new OpenAI({
       apiKey: OPEN_AI_API_KEY,
       baseURL: this.client.baseURL,
-      defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+      defaultHeaders: defaultHeadersBuilder(this.client),
     });
 
     const result = await OAIclient.files.list(query, opts).withResponse();
@@ -75,7 +75,7 @@ export class MainFiles extends ApiResource {
     const OAIclient = new OpenAI({
       apiKey: OPEN_AI_API_KEY,
       baseURL: this.client.baseURL,
-      defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+      defaultHeaders: defaultHeadersBuilder(this.client),
     });
 
     const result = await OAIclient.files.retrieve(fileId, opts).withResponse();
@@ -99,7 +99,7 @@ export class MainFiles extends ApiResource {
     const OAIclient = new OpenAI({
       apiKey: OPEN_AI_API_KEY,
       baseURL: this.client.baseURL,
-      defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+      defaultHeaders: defaultHeadersBuilder(this.client),
     });
 
     const result = await OAIclient.files.del(fileId, opts).withResponse();
@@ -123,7 +123,7 @@ export class MainFiles extends ApiResource {
     const OAIclient = new OpenAI({
       apiKey: OPEN_AI_API_KEY,
       baseURL: this.client.baseURL,
-      defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+      defaultHeaders: defaultHeadersBuilder(this.client),
     });
 
     const result = await OAIclient.files.content(fileId, opts).withResponse();
diff --git a/src/apis/images.ts b/src/apis/images.ts
index 95255c0..adff6b3 100644
--- a/src/apis/images.ts
+++ b/src/apis/images.ts
@@ -2,7 +2,7 @@ import { ApiClientInterface } from "../_types/generalTypes";
 import { ApiResource } from "../apiResource";
 import { RequestOptions } from "../baseClient";
 import { OPEN_AI_API_KEY } from "../constants";
-import { finalResponse, overrideConfig } from "../utils";
+import { defaultHeadersBuilder, finalResponse, overrideConfig } from "../utils";
 import { createHeaders } from "./createHeaders";
 import OpenAI from "openai";
 
@@ -66,7 +66,7 @@ export class Images extends ApiResource {
     const OAIclient = new OpenAI({
       apiKey: OPEN_AI_API_KEY,
       baseURL: this.client.baseURL,
-      defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+      defaultHeaders: defaultHeadersBuilder(this.client),
     });
     // @ts-ignore
     const result = await OAIclient.images.generate(body, opts).withResponse();
@@ -91,7 +91,7 @@ export class Images extends ApiResource {
     const OAIclient = new OpenAI({
       apiKey: OPEN_AI_API_KEY,
       baseURL: this.client.baseURL,
-      defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+      defaultHeaders: defaultHeadersBuilder(this.client),
     });
 
     // @ts-ignore
@@ -117,7 +117,7 @@ export class Images extends ApiResource {
     const OAIclient = new OpenAI({
       apiKey: OPEN_AI_API_KEY,
       baseURL: this.client.baseURL,
-      defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+      defaultHeaders: defaultHeadersBuilder(this.client),
     });
     // @ts-ignore
     const result = await OAIclient.images.createVariation(body, opts).withResponse();
diff --git a/src/apis/models.ts b/src/apis/models.ts
index 3c29f09..410bc4f 100644
--- a/src/apis/models.ts
+++ b/src/apis/models.ts
@@ -2,7 +2,7 @@ import { ApiClientInterface } from "../_types/generalTypes";
 import { ApiResource } from "../apiResource";
 import { RequestOptions } from "../baseClient";
 import { OPEN_AI_API_KEY } from "../constants";
-import { finalResponse, overrideConfig } from "../utils";
+import { defaultHeadersBuilder, finalResponse, overrideConfig } from "../utils";
 import { createHeaders } from "./createHeaders";
 import OpenAI from "openai";
 
@@ -23,10 +23,7 @@ export class Models extends ApiResource {
     const OAIclient = new OpenAI({
       apiKey: OPEN_AI_API_KEY,
       baseURL: this.client.baseURL,
-      defaultHeaders: {
-        ...this.client.customHeaders,
-        ...this.client.portkeyHeaders,
-      },
+      defaultHeaders: defaultHeadersBuilder(this.client)
     });
 
     const result = await OAIclient.models.list(opts).withResponse();
@@ -50,10 +47,7 @@ export class Models extends ApiResource {
     const OAIclient = new OpenAI({
       apiKey: OPEN_AI_API_KEY,
       baseURL: this.client.baseURL,
-      defaultHeaders: {
-        ...this.client.customHeaders,
-        ...this.client.portkeyHeaders,
-      },
+      defaultHeaders: defaultHeadersBuilder(this.client),
     });
 
     const result = await OAIclient.models.retrieve(model, opts).withResponse();
@@ -77,10 +71,7 @@ export class Models extends ApiResource {
     const OAIclient = new OpenAI({
       apiKey: OPEN_AI_API_KEY,
       baseURL: this.client.baseURL,
-      defaultHeaders: {
-        ...this.client.customHeaders,
-        ...this.client.portkeyHeaders,
-      },
+      defaultHeaders: defaultHeadersBuilder(this.client),
     });
 
     const result = await OAIclient.models.del(model, opts).withResponse();
diff --git a/src/apis/threads.ts b/src/apis/threads.ts
index 49f0eb9..c333826 100644
--- a/src/apis/threads.ts
+++ b/src/apis/threads.ts
@@ -3,7 +3,7 @@ import { ApiClientInterface } from "../_types/generalTypes";
 import { ApiResource } from "../apiResource";
 import { RequestOptions } from "../baseClient";
 import { OPEN_AI_API_KEY } from "../constants";
-import { finalResponse, overrideConfig } from "../utils";
+import { defaultHeadersBuilder, finalResponse, overrideConfig } from "../utils";
 import { createHeaders } from "./createHeaders";
 import OpenAI from "openai";
 
@@ -36,7 +36,7 @@ export class Threads extends ApiResource {
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
         // @ts-ignore
         const result = await OAIclient.beta.threads.create(body, opts).withResponse();
@@ -60,7 +60,7 @@ export class Threads extends ApiResource {
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.retrieve(threadId, opts).withResponse();
@@ -86,7 +86,7 @@ export class Threads extends ApiResource {
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.update(threadId, body, opts).withResponse();
@@ -110,7 +110,7 @@ export class Threads extends ApiResource {
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.del(threadId, opts).withResponse();
@@ -135,7 +135,7 @@ export class Threads extends ApiResource {
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.createAndRun(body, opts).withResponse();
@@ -173,7 +173,7 @@ export class Messages extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
         // @ts-ignore
         const result = await OAIclient.beta.threads.messages.create(threadId, body, opts).withResponse();
@@ -199,7 +199,7 @@ export class Messages extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
         // @ts-ignore
         const result = await OAIclient.beta.threads.messages.list(threadId, query, opts).withResponse();
@@ -224,7 +224,7 @@ export class Messages extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.messages.retrieve(threadId, messageId, opts).withResponse();
@@ -252,7 +252,7 @@ export class Messages extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.messages.update(threadId, messageId, body, opts).withResponse();
@@ -284,7 +284,7 @@ export class Files extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
         // @ts-ignore
         const result = await OAIclient.beta.threads.messages.files.list(threadId, messageId, query, opts).withResponse();
@@ -310,7 +310,7 @@ export class Files extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.messages.files.retrieve(threadId, messageId, fileId, opts).withResponse();
@@ -348,7 +348,7 @@ export class Runs extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.runs.create(threadId, body, opts).withResponse();
@@ -374,7 +374,7 @@ export class Runs extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
         // @ts-ignore
         const result = await OAIclient.beta.threads.runs.list(threadId, query, opts).withResponse();
@@ -399,7 +399,7 @@ export class Runs extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.runs.retrieve(threadId, runId, opts).withResponse();
@@ -426,7 +426,7 @@ export class Runs extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.runs.update(threadId, runId, body, opts).withResponse();
@@ -453,7 +453,7 @@ export class Runs extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.runs.submitToolOutputs(threadId, runId, body, opts).withResponse();
@@ -478,7 +478,7 @@ export class Runs extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.runs.cancel(threadId, runId, opts).withResponse();
@@ -509,7 +509,7 @@ export class Steps extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
         // @ts-ignore
         const result = await OAIclient.beta.threads.runs.steps.list(threadId, runId, query, opts).withResponse();
@@ -535,7 +535,7 @@ export class Steps extends ApiResource{
         const OAIclient = new OpenAI({
           apiKey: OPEN_AI_API_KEY,
           baseURL: this.client.baseURL,
-          defaultHeaders: {...this.client.customHeaders, ...this.client.portkeyHeaders},
+          defaultHeaders: defaultHeadersBuilder(this.client),
         });
     
         const result = await OAIclient.beta.threads.runs.steps.retrieve(threadId, runId, stepId, opts).withResponse();
diff --git a/src/utils.ts b/src/utils.ts
index 640f228..2d667a3 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -103,4 +103,16 @@ export function portkeyHeaders(headers:any) {
         .map(([key, value]) => [key.replace(prefix, ''), value])
     
     return Object.fromEntries(filteredHeaders)
+}
+
+export function defaultHeadersBuilder(client: any){
+	
+	const customHeaders = client.customHeaders
+	const portkeyHeaders = client.portkeyHeaders
+
+	customHeaders.hasOwnProperty("authorization") &&
+      (client.customHeaders["authorization"] =
+        "Bearer " + client.customHeaders["authorization"]);
+
+	return {...customHeaders, ...portkeyHeaders}
 }
\ No newline at end of file