diff --git a/doc/source/install-on-macosx.rst b/doc/source/install-on-macosx.rst
index c24f95ccd..cf2453ac2 100644
--- a/doc/source/install-on-macosx.rst
+++ b/doc/source/install-on-macosx.rst
@@ -46,7 +46,7 @@ Ray can be built from the repository as follows.
 
   git clone https://github.com/ray-project/ray.git
   cd ray/python
-  python setup.py install
+  python setup.py install  # Add --user if you see a permission denied error.
 
 
 Test if the installation succeeded
diff --git a/doc/source/install-on-ubuntu.rst b/doc/source/install-on-ubuntu.rst
index 8e0f2055c..394682818 100644
--- a/doc/source/install-on-ubuntu.rst
+++ b/doc/source/install-on-ubuntu.rst
@@ -54,7 +54,7 @@ Ray can be built from the repository as follows.
 
   git clone https://github.com/ray-project/ray.git
   cd ray/python
-  python setup.py install
+  python setup.py install  # Add --user if you see a permission denied error.
 
 
 Test if the installation succeeded