Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Vector -> Geoprocessing Tools -> Union worked for me. When I tried to use Merge Shapefiles option QGIS kept crashing. One thing I noticed that the output file size was much larger (5mb) compared to input files (both less than 1mb).