diff --git a/Makefile b/Makefile
index f752b90..56e82b5 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 PROJECT = softwarepublico
-VERSION ?= $(shell date +%Y.%m.%d)
+VERSION = $(shell git describe --tags || date +%Y.%d)
 
 TARBALL = dist/$(PROJECT)-$(VERSION).tar.gz
 
@@ -8,6 +8,7 @@ all:
 sdist: $(TARBALL)
 
 $(TARBALL): $(shell git ls-files)
+	@if [ -n "$$(git diff-index HEAD)" ]; then echo "Cannot proceed with uncommitted changes"; false; fi
 	mkdir -p $$(dirname $@)
 	(git archive --prefix=$(PROJECT)-$(VERSION)/ HEAD | gzip -) > $@
 
--
libgit2 0.21.2