diff --git a/README.md b/README.md
index 15a6d55a..d4f4a4dd 100644
--- a/README.md
+++ b/README.md
@@ -72,7 +72,7 @@ This section shows how to install RTAB-Map ros-pkg on **ROS Hydro/Indigo/Jade/Ki
   
     * g2o: Should be already installed by `ros-noetic-libg2o`.
 
-    * [GTSAM](https://gtsam.org/get_started/): Install via PPA to avoid building from source.
+    * [GTSAM](https://gtsam.org/get_started/): Install via PPA to avoid building from source. If you install from source, make sure to build with `cmake  -DGTSAM_BUILD_WITH_MARCH_NATIVE=OFF -DGTSAM_USE_SYSTEM_EIGEN=ON`.
     
     * [libpointmatcher](https://github.com/ethz-asl/libpointmatcher): **Recommended** if you are going to use lidars. Follow their [instructions](https://github.com/ethz-asl/libpointmatcher#quick-start) to install.