diff --git a/README.md b/README.md
index 20b777b0..04b644a4 100644
--- a/README.md
+++ b/README.md
@@ -396,6 +396,10 @@ The list of display ids can be retrieved by:
 adb shell dumpsys display   # search "mDisplayId=" in the output
 ```
 
+The secondary display may only be controlled if the device runs at least Android
+10 (otherwise it is mirrored in read-only).
+
+
 #### Turn screen off
 
 It is possible to turn the device screen off while mirroring on start with a