diff --git a/docs/releasenotes/9.1.0.rst b/docs/releasenotes/9.1.0.rst
index a0b0b5eb7..aa4b6af06 100644
--- a/docs/releasenotes/9.1.0.rst
+++ b/docs/releasenotes/9.1.0.rst
@@ -38,6 +38,9 @@ For example:
     # Or for all:
     python3 -m pip install .[docs,tests]
 
+On macOS, the last argument may need to be wrapped in quotes, e.g.
+``python3 -m pip install ".[tests]"``
+
 Therefore ``requirements.txt`` has been removed along with the ``make install-req``
 command for installing its contents.