diff --git a/src/openai/_client.py b/src/openai/_client.py
index aadf3601f2..04261feace 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"
 
@@ -536,7 +536,7 @@ 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"
 
diff --git a/src/openai/_compat.py b/src/openai/_compat.py
index 020ffeb2ca..b4b05b171b 100644
--- a/src/openai/_compat.py
+++ b/src/openai/_compat.py
@@ -149,7 +149,7 @@ def model_dump(
             exclude_defaults=exclude_defaults,
             # warnings are not supported in Pydantic v1
             warnings=True if PYDANTIC_V1 else warnings,
-            by_alias=by_alias,
+            by_alias=bool(by_alias) if by_alias is not None else False,
         )
     return cast(
         "dict[str, Any]",