diff --git a/.envrc b/.envrc
new file mode 100644
index 0000000..1d953f4
--- /dev/null
+++ b/.envrc
@@ -0,0 +1 @@
+use nix
diff --git a/Makefile b/Makefile
index e38c9c2..d6ce0d3 100644
--- a/Makefile
+++ b/Makefile
@@ -24,4 +24,4 @@ index.html : source/book.adoc $(ADOC_FILES)
 
 .PHONY: clean
 clean :
-> rm -rf $(GENERATED_ADOC_FILES)
+> rm -rf $(GENERATED_ADOC_FILES) hello-python