This is a reported bug posted on OpenMathLib/OpenBLAS#1078, and a patch was proposed at https://groups.google.com/forum/#!topic/openblas-dev/YI1of4HODmw, which has been merged to the develop branch of OpenBLAS but not in version 0.2.19. See also OpenMathLib/OpenBLAS#1098.