Fix build on GHC 7.8
Fix build on GHC 7.8

MichielDerhaeg/stack,deech/stack,achernyak/stack,Heather/stack,mathhun/stack,AndreasPK/stack,phadej/stack,keent/stack,rubik/stack,keent/stack,juhp/stack,sjakobi/stack,mrkkrp/stack,martin-kolinek/stack,deech/stack,rubik/stack,AndreasPK/stack,mathhun/stack,achernyak/stack,anton-dessiatov/stack,luigy/stack,sjakobi/stack,narrative/stack,AndrewRademacher/stack,harendra-kumar/stack,rvion/stack,luigy/stack,MichielDerhaeg/stack,Fuuzetsu/stack,mrkkrp/stack,martin-kolinek/stack,vigoo/stack,Fuuzetsu/stack,anton-dessiatov/stack,juhp/stack,vigoo/stack,narrative/stack,harendra-kumar/stack,Blaisorblade/stack,AndrewRademacher/stack,phadej/stack,rvion/stack,Blaisorblade/stack,Heather/stack