The Wikipedia article for real value says
In economics, a nominal value is an economic value expressed in historical nominal monetary terms. By contrast, a real value is a value that has been adjusted from a nominal value to remove the effects of general price level changes over time and is thus measured in terms of the general price level in some reference year (the base year).
Here the Wikipedia link for general price level changes takes me straight to the article for inflation. But then the Wikipedia article for deflation says
Economists generally believe that deflation is a problem in a modern economy because it increases the real value of debt
This sounds like a contradiction to me, because by the first definition, the real value of debt remains constant under deflation.
Can someone explain this?