Pdflatex with output directory and synctex

I am trying to use pdflatex with synctex and output directory. When I use these features separately, they work (commands 1 and 2). But when I use them together, the synctex.gz file is not generated (command 3 ends up doing the same as command 2).

1. pdflatex -synctex=1
2. pdflatex -output-directory=/tmp/tmp123456
3. pdflatex -synctex=1 -output-directory=/tmp/tmp123456

Is this a bug? How to run pdflatex with custom output directory and generating synctex files?