diff --git a/src/openai/_client.py b/src/openai/_client.py
index 0399bbf742..5474f2c635 100644
--- a/src/openai/_client.py
+++ b/src/openai/_client.py
@@ -161,7 +161,7 @@ def __init__(
         self.websocket_base_url = websocket_base_url
 
         if base_url is None:
-            base_url = os.environ.get("OPENAI_BASE_URL")
+            base_url = os.environ.get("OPENAI_BASE_URL") or None
         if base_url is None:
             base_url = f"https://api.openai.com/v1"
 
@@ -518,7 +518,7 @@ def __init__(
         self.websocket_base_url = websocket_base_url
 
         if base_url is None:
-            base_url = os.environ.get("OPENAI_BASE_URL")
+            base_url = os.environ.get("OPENAI_BASE_URL") or None
         if base_url is None:
             base_url = f"https://api.openai.com/v1"