Used the lines at Toronto YYZ. Wife as a US PR and Nexus holder was recognized with glasses without issue. Machine didn't recognize me, asked to insert documents, I tried to scan the back of my Nexus card but no luck, by the time I pulled out my passport it was flashing red and said something along the lines of Check with Officer. I waited for it to clear, then took off my glasses, at which point it turned on again and recognized me. Went to the lineup, was directed to a lane by an airport agent, went to a lane, where the officer took our cards, including my wife's US green card and took her photo. He asked if I was a US citizen, I said yes and he waved us through (no photo needed for me). Total time from entry into the NEXUS area to exit was 3 minutes.