diff --git a/README.md b/README.md
index 06a3e0d802..05026d881c 100644
--- a/README.md
+++ b/README.md
@@ -34,7 +34,7 @@ npm install @aspnet/signalr-client --registry https://dotnet.myget.org/f/aspnetc
 
 ## Building from source
 
-To run a complete build on command line only, execute `build.cmd` or `build.sh` without arguments.
+To run a complete build on command line only, execute `build.cmd` or `build.sh` without arguments. The build requires NodeJS (6.11 or newer) and npm to be installed on the machine.
 
 Before opening this project in Visual Studio or VS Code, execute `build.cmd /t:Restore` (Windows) or `./build.sh /t:Restore` (Linux/macOS).
 This will execute only the part of the build script that downloads and initializes a few required build tools and packages.