45-year-old female, BMI 40 kg/m2 with history of sleeve gastrectomy presenting for conversion to gastric bypass due to weight regain and reflux. Patient was brought to the OR and placed in supine position. The abdomen was entered via optical trocar at Palmer's point. Trocars were placed to the left and right of the umbilicus and in the RUQ. The jejunojejunostomy was created in standard stapled fashion. The lateral edge of the sleeve was dissected using ultrasonic energy to enter the lesser sac. A peri-gastric dissection was performed to create a tunnel underneath the sleeve. The sleeve was divided 5 cm from the GE junction. A gastrotomy was made using ultrasonic energy, however we did not feel the characteristic 'pop' into the lumen. A submucosal false passage was unknowingly made. The gastrojejunal anastomosis was then created from the false passage to the roux limb. When we attempted to pass the bougie through the GJ to calibrate the anastomosis, it would not pass, and we could see that we had stapled to the submucosal false passage and not the true lumen of the stomach. We then divided the pouch proximally and the roux limb distally. We repeated our gastrotomy, this time definitively popping into the lumen and visualizing mucosa. We performed our standard GJ anastomosis, passing the bougie through the pouch into the roux limb and sutured the anastomosis closed. Patient had an uneventful post-operative course and was discharged on POD 1. She has since recovered without issue.