diff --git a/rabin/rabin_dedup.c b/rabin/rabin_dedup.c
index d36fc11..aed8989 100755
--- a/rabin/rabin_dedup.c
+++ b/rabin/rabin_dedup.c
@@ -92,7 +92,7 @@ dedupe_min_blksz(int rab_blk_sz)
 {
 	uint32_t min_blk;
 
-	min_blk = 1 << (rab_blk_sz + RAB_BLK_MIN_BITS - 1);
+	min_blk = (1 << (rab_blk_sz + RAB_BLK_MIN_BITS)) - 1024;
 	return (min_blk);
 }
 
@@ -180,7 +180,7 @@ create_dedupe_context(uint64_t chunksize, uint64_t real_chunksize, int rab_blk_s
 	ctx->fixed_flag = fixed_flag;
 	ctx->rabin_break_patt = 0;
 	ctx->rabin_poly_avg_block_size = 1 << (rab_blk_sz + RAB_BLK_MIN_BITS);
-	ctx->rabin_avg_block_mask = ((ctx->rabin_poly_avg_block_size - 1) >> 1);
+	ctx->rabin_avg_block_mask = ((ctx->rabin_poly_avg_block_size - 1) >> 2);
 	ctx->rabin_poly_min_block_size = dedupe_min_blksz(rab_blk_sz);
 	ctx->delta_flag = 0;