diff --git a/README.rst b/README.rst
index 2a600a7ce..1a0aab743 100644
--- a/README.rst
+++ b/README.rst
@@ -25,5 +25,5 @@ The ``master`` branch is always the development branch. If a new server version
 Building
 --------
 
-Enter any manual directory, then run ``make html``. The result can be found in the ``_build/html`` subdirectory.
+Make sure that Sphinx is installed (e.g. sudo yum install python-sphinx), then enter any manual directory, then run ``make html``. The result can be found in the ``_build/html`` subdirectory.