diff --git a/aider/sendchat.py b/aider/sendchat.py
index e767e29ce..7e12e36c9 100644
--- a/aider/sendchat.py
+++ b/aider/sendchat.py
@@ -1,5 +1,6 @@
 import hashlib
 import json
+import os
 
 import backoff
 
@@ -57,6 +58,9 @@ def send_completion(
         temperature=temperature,
         stream=stream,
     )
+    
+    if model_name.startswith("deepseek/") and "DEEPSEEK_API_BASE" in os.environ:
+        kwargs["base_url"] = os.environ["DEEPSEEK_API_BASE"]
     if functions is not None:
         kwargs["functions"] = functions
     if extra_headers is not None: