diff --git a/Makefile b/Makefile
index 0b1a43435..101cfca2c 100644
--- a/Makefile
+++ b/Makefile
@@ -56,7 +56,7 @@ clean-backupfiles:
 
 clean-generated:
 	find . -name '.DS_Store' -exec rm -f {} +
-	rm -f doc/_build/
+	rm -rf doc/_build/
 	rm -f sphinx/pycode/*.pickle
 	rm -f utils/*3.py*
 	rm -f utils/regression_test.js