QGIS 3 Display negative values bar diagrams

Suppose I have a dataset with an id (for each geographic entities) and 2 numeric fields NUM1 and NUM2. These numeric fields have positive and negative values.

When I use bar diagrams, only theses cases are displayed :

• NUM1 is positive, NUM2 is positive
• NUM1 is positive, NUM2 is negative
• NUM1 is negative, NUM2 is positive

If NUM1 and NUM2 are negative, the bar diagrams are missing. Same story if we only use one numeric field. Is it a bug? How to display negative values in bar diagrams?