diff --git a/libntfs/runlist.c b/libntfs/runlist.c
index 0e6b2c75..7b8968fe 100644
--- a/libntfs/runlist.c
+++ b/libntfs/runlist.c
@@ -1035,7 +1035,7 @@ s64 ntfs_rl_pread(const ntfs_volume *vol, const runlist_element *rl,
 	/* Seek in @rl to the run containing @pos. */
 	for (ofs = 0; rl->length && (ofs + (rl->length <<
 			vol->cluster_size_bits) <= pos); rl++)
-		ofs += rl->length * vol->cluster_size;
+		ofs += (rl->length << vol->cluster_size_bits);
 	/* Offset in the run at which to begin reading. */
 	ofs = pos - ofs;
 	for (total = 0LL; count; rl++, ofs = 0) {
@@ -1119,7 +1119,7 @@ s64 ntfs_rl_pwrite(const ntfs_volume *vol, const runlist_element *rl,
 	/* Seek in @rl to the run containing @pos. */
 	for (ofs = 0; rl->length && (ofs + (rl->length <<
 			vol->cluster_size_bits) <= pos); rl++)
-		ofs += rl->length * vol->cluster_size;
+		ofs += (rl->length << vol->cluster_size_bits);
 	/* Offset in the run at which to begin writing. */
 	ofs = pos - ofs;
 	for (total = 0LL; count; rl++, ofs = 0) {