Fix build on GHC 7.8
Fix build on GHC 7.8

AndrewRademacher/stack,juhp/stack,Fuuzetsu/stack,AndrewRademacher/stack,anton-dessiatov/stack,Blaisorblade/stack,phadej/stack,MichielDerhaeg/stack,AndreasPK/stack,deech/stack,mrkkrp/stack,juhp/stack,martin-kolinek/stack,MichielDerhaeg/stack,Fuuzetsu/stack,Blaisorblade/stack,anton-dessiatov/stack,mrkkrp/stack,Heather/stack,Heather/stack,AndreasPK/stack,deech/stack,phadej/stack,sjakobi/stack,sjakobi/stack,martin-kolinek/stack