Crash with BRepFilletAPI_MakeFillet

Hi guys! I have a simple cube and would like to make a fillet on one of the edges. Here's the code I'm using

BRepFilletAPI_MakeFillet mkFillet(body, ChFi3d_Rational);

TopExp_Explorer aEdgeExplorer;
aEdgeExplorer.Init(body, TopAbs_EDGE, 0);
while (aEdgeExplorer.More())
{
TopoDS_Edge aEdge = TopoDS::Edge(aEdgeExplorer.Current());

mkFillet.Add(0.01, aEdge);
break;
}
mkFillet.Build();
currentShape = mkFillet.Shape();

As soon as the last line is executed, the program crashes. Any idea why? Many thanks in advance!