diff --git a/Makefile b/Makefile
index 0e2ac22721226c7a4afb3742a087efc54f853bc9..e5f49e52c59f0dd1f523c087d92b869f3c6879e3 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 all: html
 
-build/%.ipynb: %.md $(wildcard d2lzh/*)
+build/%.ipynb: %.md build/env.yml $(wildcard d2lzh/*)
 	@mkdir -p $(@D)
 	cd $(@D); python ../utils/md2ipynb.py ../../$< ../../$@