diff --git a/buildconf.bat b/buildconf.bat
index 1499ca0b13..beecb6f621 100644
--- a/buildconf.bat
+++ b/buildconf.bat
@@ -5,7 +5,10 @@ REM $Date$
 
 REM create ca-bundle.h
 echo /* This file is generated automatically */ >lib\ca-bundle.h
-echo #define CURL_CA_BUNDLE getenv("CURL_CA_BUNDLE") >>lib\ca-bundle.h
+echo #ifndef CURL_CA_BUNDLE >>lib\ca-bundle.h
+echo #define CURL_CA_BUNDLE getenv("CURL_CA_BUNDLE") >>lib\ca-bundle.h
+echo #endif >>lib\ca-bundle.h
+
 
 REM create hugehelp.c
 copy src\hugehelp.c.cvs src\hugehelp.c