diff --git a/Makefile b/Makefile
index aad8996a..f715deae 100644
--- a/Makefile
+++ b/Makefile
@@ -29,7 +29,7 @@ themes.json: $(wildcard static/*/config.json) help/fr/misc-scss.page
 %.css: export LC_ALL=C.UTF-8
 .SECONDEXPANSION:
 %.css: %.scss $(wildcard static/includes/*.scss) static/includes/_data_uris.scss static/grandlyon-gnm/_data_uris.scss static/lille/_data_uris.scss static/lomme/_data_uris.scss static/hellemmes/_data_uris.scss static/toodego/_data_uris.scss $$(wildcard $$(@D)/*.scss)
-	sassc -mauto $< $@
+	sassc --sourcemap $< $@
 
 css: $(shell python get_themes.py) static/portal-agent/css/agent-portal.css
 	rm -rf static/*/.sass-cache/