diff --git a/Makefile b/Makefile
index e04103d..f620f4e 100644
--- a/Makefile
+++ b/Makefile
@@ -79,7 +79,7 @@ lint: lint/isort-check lint/flake8
 docs/clean:
 	rm -rf $(DOCS_DIR)/build/
 
-docs:
+docs: virtualenv
 	cd $(DOCS_DIR) && SPHINXBUILD=$(SPHINXBUILD) make html
 
 release/clean:
diff --git a/requirements/requirements-documentation.txt b/requirements/requirements-documentation.txt
index b5cb07a..3f3273a 100644
--- a/requirements/requirements-documentation.txt
+++ b/requirements/requirements-documentation.txt
@@ -1 +1,3 @@
 m2r==0.2.1
+Sphinx
+sphinx-rtd-theme