diff --git a/docs/Makefile b/docs/Makefile
index 1a912039e..510c4e2cc 100644
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -42,7 +42,7 @@ clean:
 	-rm -rf $(BUILDDIR)/*
 
 html:
-	$(SPHINXBUILD) -b html $(ALLSPHINXOPTS) $(BUILDDIR)/html
+	$(SPHINXBUILD) -b html -W $(ALLSPHINXOPTS) $(BUILDDIR)/html
 	@echo
 	@echo "Build finished. The HTML pages are in $(BUILDDIR)/html."