diff --git a/compress42.c b/compress42.c

index 4d33342..495bdf3 100644

--- a/compress42.c

+++ b/compress42.c

@@ -1373,7 +1373,7 @@ compress(fdin, fdout)

 		REG11	int			boff;

 		REG12	int			n_bits;

 		REG13	int			ratio;

-		REG14	long		checkpoint;

+		REG14	unsigned long long	checkpoint;

 		REG15	code_int	extcode;

 		union

 		{