diff --git a/setup.cfg b/setup.cfg
index 8d04412..217c8ee 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -58,9 +58,10 @@ test =
   pytest-ordering
   pytest-cov
 docs =
-  sphinx
+  sphinx<7.0.0  
   sphinx_rtd_theme
   m2r2
+# pin sphinx because 7.0 currently not compatible with rtd theme
 
 [options.packages.find]
 where = src