Problem with stepper motor steps

I have been accurately controlling a stepper motor with the Arduino Mega and a motor shield and have been able to rotate 1 degree per step. Recently, I changed my setup a little bit to include gears, but for some reason, the shaft of the motor now rotates 2 degrees per step. I have not changed anything in the programming of the Arduino; I have just changed the physical setup. Is this a known problem? Thanks.

Its nearly universal to have 1.8 degree steps, so I'm not convinced... Perhaps it was mis-stepping before (0.9 degrees) and is now behaving correctly. If the gearing has reduced the torque the motor has to produce that would support this hypothesis... Are you full stepping, half-stepping or wave-stepping? How close to the rated torque are you loading the motor and how fast are you trying to turn it?