diff --git a/scripts/screenshot-android.sh b/scripts/screenshot-android.sh
index abbea08..60300c1 100755
--- a/scripts/screenshot-android.sh
+++ b/scripts/screenshot-android.sh
@@ -1,2 +1,7 @@
 #!/usr/bin/env bash
+if [ -z "$DEVICE" ]; then
+  echo "Error: DEVICE environment variable is not set."
+  echo "Usage: DEVICE=emulator-5554 ./screenshot-android.sh"
+  exit 1
+fi
 exec adb -s $DEVICE exec-out screencap -p > screenshot-emulator-$(date +%s).png
\ No newline at end of file