Merge pull request #233 from NaokiTsuchiya/fix-type #1190

Job	Run time
ci / PHPUnit (7.2, highest, ubuntu-latest, false)	18s
ci / PHPUnit (7.2, lowest, ubuntu-latest, false)	18s
ci / PHPUnit (7.3, highest, ubuntu-latest, false)	23s
ci / PHPUnit (7.3, lowest, ubuntu-latest, false)	22s
ci / PHPUnit (7.4, highest, ubuntu-latest, false)	18s
ci / PHPUnit (7.4, lowest, ubuntu-latest, false)	18s
ci / PHPUnit (8.0, highest, ubuntu-latest, false)	22s
ci / PHPUnit (8.0, lowest, ubuntu-latest, false)	18s
ci / PHPUnit (8.1, highest, ubuntu-latest, false)	21s
ci / PHPUnit (8.1, lowest, ubuntu-latest, false)	31s
ci / PHPUnit (8.2, highest, ubuntu-latest, false)	19s
ci / PHPUnit (8.2, lowest, ubuntu-latest, false)	18s
ci / PHPUnit (8.3, highest, ubuntu-latest, false)	21s
ci / PHPUnit (8.3, lowest, ubuntu-latest, false)	18s
ci / PHPUnit (8.4, windows-latest, highest, false)	52s
ci / PHPUnit (8.4, ubuntu-latest, highest, false)	18s
ci / PHPUnit (8.4, ubuntu-latest, lowest, false)	18s
	6m 13s

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