diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -159,6 +159,7 @@ i18n/hg.pot: $(PYFILES) $(DOCFILES) i18n
 # Packaging targets
 
 osx:
+	rm -rf build/mercurial
 	/usr/bin/python2.7 setup.py install --optimize=1 \
 	  --root=build/mercurial/ --prefix=/usr/local/ \
 	  --install-lib=/Library/Python/2.7/site-packages/