Your Android phone might be uploading your photos to Google without you knowing it.

A journalist at the Nashville Business Journal discovered this strange quirk of the Google Photos app, and showed how your personal photos might still get uploaded to the web without you knowing it. In the video above, David Arnott uninstalls the Google Photos app from his phone, but the photo he took of his coffee mug still wound up being synced into his account on the web.

Sure, he turned on the backup sync before uninstalling the app. But isn't it reasonable to expect the phone to not do that after the app has been removed? In the video, he demonstrates it with just a quick photo of his coffee mug, but Arnott made the surprising discovery, initially, with dozens of personal and family photos he took—all uploaded without his knowledge.

When he first made this discovery earlier this week, he went on a Twitter "hate-tweet" spree:

Something kind of annoying/scary I discovered with Google Photos on my Android phone. 1) Months ago, I downloaded the app to play with it — David A. Arnott (@ArnottACBJ) July 8, 2015

2)but I didn't like it and so uninstalled the app after just a few days. This evening, I went back to Google Photos on my laptop and found — David A. Arnott (@ArnottACBJ) July 8, 2015

3)a crap-ton of pictures Id taken in the interim. It seems that even AFTER I UNINSTALLED the Google Photos app it was still syncing pictures — David A. Arnott (@ArnottACBJ) July 8, 2015

4)from my phone when on WiFi. Obviously a problem. — David A. Arnott (@ArnottACBJ) July 8, 2015

5)I deleted all those photos, re-installed the app, found the syncing option and turned it off. — David A. Arnott (@ArnottACBJ) July 8, 2015

6)Because I don't trust Google Photos anymore, I'm keeping the app to make sure the syncing is turned off -- which is DEEPLY stupid. — David A. Arnott (@ArnottACBJ) July 8, 2015

In response to an email, Google told Arnott, "The backup was as intended" and that the setting would have to be turned off in the phone's Google Play Services settings. As AndroidHeadlines.com explains, Google Photos' settings are interconnected with the phone's Google Play Services, although unlike applications, Google Play keeps Google Photos' settings even after it's uninstalled.

If you're an Android user and want to avoid having your personal photos on your phone from making it onto the web (even in your own personal Google account), better check now and change those settings.