diff --git a/README.md b/README.md
index 829c38f84ce4fad9f10d4273a4f4d6fa569bd6b6..70f7fd23329b0bdde042eca6ba00dddaf6d5ef46 100644
--- a/README.md
+++ b/README.md
@@ -70,6 +70,10 @@ version of the mean shift grouping algorithm with:
     cd LSMTool
     python setup.py install --build_c_extentions
 
+Note that the C++ version will give slightly different results compared to the
+Python version, but such differences are not expected to be important
+in practice.
+
 ### Testing
 
 You can test that the installation worked with: