Failure [INSTALL_FAILED_INVALID_APK]

Failure [INSTALL_FAILED_INVALID_APK]

When I click to run a project I just created in Android Studio 0.2.10 and
select my phone I get this error:
Waiting for device.
Target device: 0123456789ABCDEF
Uploading file
local path:
/Users/Rui/AndroidStudioProjects/FirstAppProject/FirstApp/build/apk/FirstApp-debug-unaligned.apk
remote path: /data/local/tmp/rui.firstapp
Installing rui.firstapp
DEVICE SHELL COMMAND: pm install -r "/data/local/tmp/rui.firstapp"
pkg: /data/local/tmp/rui.firstapp
Failure [INSTALL_FAILED_INVALID_APK]
Any Idea of what it might be?