diff --git a/docs/INSTALL.rst b/docs/INSTALL.rst
index 3172c21..f96bf6a 100644
--- a/docs/INSTALL.rst
+++ b/docs/INSTALL.rst
@@ -12,7 +12,7 @@
 
 - doxygen
 - graphviz
-- sphinx >= 1.3
+- sphinx >= 4.0
 - sphinxcontrib-doxylink
 
 Build