fix compilation error #1549

Job	Run time
macos-latest: clang++ Release Threads	31m 8s
macos-latest: clang++ Release OneTBB	2m 34s
macos-latest: clang++ Release PaRSEC	4m 58s
ubuntu-20.04: /usr/bin/g++-9 Release Threads	29m 34s
ubuntu-20.04: /usr/bin/g++-9 Release OneTBB	2m 20s
ubuntu-20.04: /usr/bin/g++-9 Release PaRSEC	2m 36s
macos-latest: clang++ Debug Threads	19m 23s
macos-latest: clang++ Debug OneTBB	4m 33s
macos-latest: clang++ Debug PaRSEC	2m 53s
ubuntu-20.04: /usr/bin/g++-9 Debug Threads	30m 38s
ubuntu-20.04: /usr/bin/g++-9 Debug OneTBB	2m 55s
ubuntu-20.04: /usr/bin/g++-9 Debug PaRSEC	3m 20s
	2h 16m 52s

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