LD_LIBRARY_PATH sometimes just gets randomly unset

At first I thought I had screwed something up in my .qbs file, but when I looked at Run > Environment, LD_LIBRARY_PATH was not set. I have three Qt applications in this Qbs project, and it's completely random as to which one will have LD_LIBRARY_PATH unset from its run environment.

Unfortunately the project I have cannot be shared, and I can't reliably reproduce this.

My workaround so far has been to copy the value from the run environment of another project.