Rule-based labeling and the Data defined placement options are not working together (QGIS 2.12, 2.14)

After setting "Rule-based labeling" to my layer (new feature since QGIS 2.12), my data defined labeling is not working any more (see labeling tools on the right side):

Going back to "Show labels for this layer", it works fine (see labeling tools on the right side):