diff --git a/doc/install-on-macosx.md b/doc/install-on-macosx.md
index 186f557e1..87989396f 100644
--- a/doc/install-on-macosx.md
+++ b/doc/install-on-macosx.md
@@ -24,12 +24,11 @@ sudo pip install numpy typing funcsigs subprocess32 protobuf==3.0.0a2 boto3 boto
 
 ### Build
 
-Then run the setup scripts. Note that `./setup.sh` could take about 10 minutes
-to run.
+Then run the setup scripts.
 
 ```
 cd ray
-./setup.sh # Build all necessary third party libraries (e.g., gRPC and Apache Arrow).
+./setup.sh # Build all necessary third party libraries (e.g., gRPC and Apache Arrow). This may take about 10 minutes.
 ./build.sh # Build Ray.
 source setup-env.sh # Add Ray to your Python path.
 ```
diff --git a/doc/install-on-ubuntu.md b/doc/install-on-ubuntu.md
index ab0d37791..ab4d11ab4 100644
--- a/doc/install-on-ubuntu.md
+++ b/doc/install-on-ubuntu.md
@@ -20,12 +20,11 @@ sudo pip install ipython typing funcsigs subprocess32 protobuf==3.0.0a2 boto3 bo
 
 ### Build
 
-Then run the setup scripts. Note that `./setup.sh` could take about 10 minutes
-to run.
+Then run the setup scripts.
 
 ```
 cd ray
-./setup.sh # Build all necessary third party libraries (e.g., gRPC and Apache Arrow).
+./setup.sh # Build all necessary third party libraries (e.g., gRPC and Apache Arrow). This may take about 10 minutes.
 ./build.sh # Build Ray.
 source setup-env.sh # Add Ray to your Python path.
 ```