diff --git a/Makefile b/Makefile
index 460bf56..2712ef1 100644
--- a/Makefile
+++ b/Makefile
@@ -4,5 +4,6 @@ cover:
 	cat cover.tmp.out | grep -v "encode_optype.go" > cover.out; \
 	rm cover.tmp.out
 
+.PHONY: cover-html
 cover-html: cover
 	go tool cover -html=cover.out