tst_QStorageInfo fails on Linux

T_PLUGIN_PATH=/home/marc/Qt/qtbase-build/plugins LD_LIBRARY_PATH=/home/marc/Qt/qtbase-build/lib${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}  ./tst_qstorageinfo 
********* Start testing of tst_QStorageInfo *********
Config: Using QtTest library 5.6.0, Qt 5.6.0 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 4.9.3 20150116 (prerelease))
PASS   : tst_QStorageInfo::initTestCase()
PASS   : tst_QStorageInfo::defaultValues()
PASS   : tst_QStorageInfo::operatorEqual()
PASS   : tst_QStorageInfo::operatorNotEqual()
PASS   : tst_QStorageInfo::root()
PASS   : tst_QStorageInfo::currentStorage()
PASS   : tst_QStorageInfo::storageList()
FAIL!  : tst_QStorageInfo::tempFile() 'free != storage2.bytesFree()' returned FALSE. ()
   Loc: [/home/marc/Qt/qtbase/tests/auto/corelib/io/qstorageinfo/tst_qstorageinfo.cpp(171)]
FAIL!  : tst_QStorageInfo::caching() 'free != storage2.bytesFree()' returned FALSE. ()
   Loc: [/home/marc/Qt/qtbase/tests/auto/corelib/io/qstorageinfo/tst_qstorageinfo.cpp(196)]
PASS   : tst_QStorageInfo::cleanupTestCase()
Totals: 8 passed, 2 failed, 0 skipped, 0 blacklisted
********* Finished testing of tst_QStorageInfo *********