diff --git a/src/pip_requirements.txt b/src/pip_requirements.txt
index df60e2c..64b1dea 100644
--- a/src/pip_requirements.txt
+++ b/src/pip_requirements.txt
@@ -1,3 +1,4 @@
 dnspython3>=1.12.0
 alabaster>=0.6.2
+Sphinx>=1.2.3