diff --git a/documentation/library-reference/source/system/operating-system.rst b/documentation/library-reference/source/system/operating-system.rst
index e7cc5326b..5035b89d8 100644
--- a/documentation/library-reference/source/system/operating-system.rst
+++ b/documentation/library-reference/source/system/operating-system.rst
@@ -413,6 +413,9 @@ System library's operating-system module.
       command as parsed by the shell. Example: ``"/bin/ls -l"`` or
       ``#["/bin/ls", "-l"]``
 
+      .. note:: On Windows this must be a :drm:`<string>`, not a sequence of
+                strings.
+
    :parameter #key under-shell?: An instance of :drm:`<boolean>`. If true (the
       default), use a shell to invoke the *command*. On Unix systems this is
       equivalent to ``/bin/sh -c '...command...'``. On Windows the
diff --git a/documentation/sphinx-extensions b/documentation/sphinx-extensions
index 632828b93..05804f149 160000
--- a/documentation/sphinx-extensions
+++ b/documentation/sphinx-extensions
@@ -1 +1 @@
-Subproject commit 632828b9319d91293401350038e932f153229e57
+Subproject commit 05804f14913ea7cbd1ce6c7d0d7b540dbaae8ca6