The documentation claims this:
"If the shapefile does not have an associated projection, then the shapefile is assumed to be WGS84"
That does not seem to be quite true at least for me with version 1.8.37 on 64-bit Windows 7 platform. Import of shapefiles in WGS84 fails for me if .prj file is not found. Not a big issue at all but contradicts with the documentation.