diff --git a/docs/requirements.txt b/docs/requirements.txt
index ba3a3ae172dc6be8481c3ad578d79f38285417f6..fe04b64ba557e7f26295bde6b23e9ff49010df3a 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,3 +1,4 @@
+sphinx>=6
 pysolar==0.10.0
 docopt
-nbsphinx
+nbsphinx
\ No newline at end of file