diff --git a/build-py-project-within-miniconda.sh b/build-py-project-within-miniconda.sh
index 2934dcbe5c4776de2a3fbdaa3a4f1cb34874c6a1..cb9ae400044d2ed02ed49dd42bbde872f927196e 100644
--- a/build-py-project-within-miniconda.sh
+++ b/build-py-project-within-miniconda.sh
@@ -12,6 +12,22 @@ echo "git status:"
 git status -s
 echo "-----------------------------------------------"
 
+# {{{ clean up
+
+rm -Rf .env
+rm -Rf build
+find . -name '*.pyc' -delete
+
+rm -Rf env
+git clean -fdx -e siteconf.py -e boost-numeric-bindings $GIT_CLEAN_EXCLUDE
+
+if test `find "siteconf.py" -mmin +1`; then
+  echo "siteconf.py older than a minute, assumed stale, deleted"
+  rm -f siteconf.py
+fi
+
+# }}}
+
 if [ "$(uname)" = "Darwin" ]; then
   PLATFORM=MacOSX
 else