diff --git a/README.md b/README.md
index 7180efd5a..f9e82a237 100644
--- a/README.md
+++ b/README.md
@@ -152,7 +152,7 @@ pip3 install --upgrade -r requirements.txt
 Create a `.env` file in the root directory and add your API key:
 
 ```bash
-CHATGPT_API_KEY=your_openai_key_here
+OPENAI_API_KEY=your_openai_key_here
 ```
 
 ### 3. Run PageIndex on your PDF
diff --git a/pageindex/utils.py b/pageindex/utils.py
index dc7acd888..45a321339 100644
--- a/pageindex/utils.py
+++ b/pageindex/utils.py
@@ -17,7 +17,7 @@
 from pathlib import Path
 from types import SimpleNamespace as config
 
-CHATGPT_API_KEY = os.getenv("CHATGPT_API_KEY")
+OPENAI_API_KEY = os.getenv("OPENAI_API_KEY")
 
 def count_tokens(text, model=None):
     if not text:
@@ -26,7 +26,7 @@ def count_tokens(text, model=None):
     tokens = enc.encode(text)
     return len(tokens)
 
-def ChatGPT_API_with_finish_reason(model, prompt, api_key=CHATGPT_API_KEY, chat_history=None):
+def ChatGPT_API_with_finish_reason(model, prompt, api_key=OPENAI_API_KEY, chat_history=None):
     max_retries = 10
     client = openai.OpenAI(api_key=api_key)
     for i in range(max_retries):
@@ -58,7 +58,7 @@ def ChatGPT_API_with_finish_reason(model, prompt, api_key=CHATGPT_API_KEY, chat_
 
 
 
-def ChatGPT_API(model, prompt, api_key=CHATGPT_API_KEY, chat_history=None):
+def ChatGPT_API(model, prompt, api_key=OPENAI_API_KEY, chat_history=None):
     max_retries = 10
     client = openai.OpenAI(api_key=api_key)
     for i in range(max_retries):
@@ -86,7 +86,7 @@ def ChatGPT_API(model, prompt, api_key=CHATGPT_API_KEY, chat_history=None):
                 return "Error"
             
 
-async def ChatGPT_API_async(model, prompt, api_key=CHATGPT_API_KEY):
+async def ChatGPT_API_async(model, prompt, api_key=OPENAI_API_KEY):
     max_retries = 10
     messages = [{"role": "user", "content": prompt}]
     for i in range(max_retries):