diff --git a/requirements.txt b/requirements.txt
index 39e361b2ed09e2c28e9e78d920c01f34737d6805..ba3a3ae172dc6be8481c3ad578d79f38285417f6 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,3 @@
 pysolar==0.10.0
 docopt
+nbsphinx