Mary has just stated that normally, as price rises, supply will increase. Her teacher grimaces. Why?

This is a question for my micro econ cl, and I am unsure what is wrong with the statement that Mary made. Supply is a positive slope, and demand is negative. So therefore, as price rises, supply should increase as well. With Price being on the y axis and quantity on the x axis of course. Can anyone help me? Any help is greatly appreciated. Thanks in advance