adb pull -> device not found

I have a rooted phone and running adb in root mode. I used adb shell to successfully access the phone. I can browse directorys, even those who require root. When i try to use: ``` adb pull /data/data/my.app.path/databases/mydatabase.db /home/admin/Desktop/ ``` I get the following error: ``` error: device not found ``` The adb shell stays connected and i can go on browsing the sdcard. Can anyone tell me where this error comes from and how i can fix it to pull the file?