diff --git a/Makefile b/Makefile
index 3e18b143..71c4653b 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 all: test
 
 clean:
-	rm -rf build dist *.egg-info/ .tox/ target/ venv/
+	rm -rf build dist *.egg-info/ .tox/ target/ venv/ instance/
 	find . -name '*.pyc' -delete
 	find . -name '__pycache__' -delete