diff --git a/README.md b/README.md
index 26beaaf..764bea2 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,12 @@ make && make install
 ```bash
 pip install --upgrade https://github.com/unlimblue/KNN_CUDA/releases/download/0.2/KNN_CUDA-0.2-py3-none-any.whl
 ```
+And then, make sure [`ninja`](https://ninja-build.org/) has been installed:
+  1. see [https://pytorch.org/tutorials/advanced/cpp_extension.html](https://pytorch.org/tutorials/advanced/cpp_extension.html)
+  2. **or just**:
+```bash
+wget -P /usr/bin https://github.com/unlimblue/KNN_CUDA/raw/master/ninja
+```
 
 
 #### Usage