diff --git a/scipy/weave/build_tools.py b/scipy/weave/build_tools.py
index b990f33..57a5a8e 100644
--- a/scipy/weave/build_tools.py
+++ b/scipy/weave/build_tools.py
@@ -228,7 +228,7 @@ def build_extension(module_path,compiler_name = '',build_dir = None,

     # configure temp and build directories
     temp_dir = configure_temp_dir(temp_dir)
-    build_dir = configure_build_dir(module_dir)
+    build_dir = configure_build_dir(build_dir or module_dir)

     # dag. We keep having to add directories to the path to keep
     # object files separated from each other.  gcc2.x and gcc3.x C++
--
1.8.1.2