diff --git a/libntfs-3g/runlist.c b/libntfs-3g/runlist.c
index 7e158d44..c83c2b7d 100644
--- a/libntfs-3g/runlist.c
+++ b/libntfs-3g/runlist.c
@@ -939,40 +939,45 @@ mpa_err:
 				"attribute.\n");
 		goto err_out;
 	}
-	/* Setup not mapped runlist element if this is the base extent. */
-	if (!attr->lowest_vcn) {
-		VCN max_cluster;
 
-		max_cluster = ((sle64_to_cpu(attr->allocated_size) +
+	/*
+	 * If this is the base of runlist (if 'lowest_vcn' is 0), then
+	 * 'allocated_size' is valid, and we can use it to compute the total
+	 * number of clusters across all extents.  If the runlist covers all
+	 * clusters, then it fits into a single extent and we can terminate
+	 * the runlist with LCN_NOENT.  Otherwise, we must terminate the runlist
+	 * with LCN_RL_NOT_MAPPED and let the caller look for more extents.
+	 */
+	if (!attr->lowest_vcn) {
+		VCN num_clusters;
+
+		num_clusters = ((sle64_to_cpu(attr->allocated_size) +
 				vol->cluster_size - 1) >>
-				vol->cluster_size_bits) - 1;
-		/*
-		 * A highest_vcn of zero means this is a single extent
-		 * attribute so simply terminate the runlist with LCN_ENOENT).
-		 */
-		if (deltaxcn) {
+				vol->cluster_size_bits);
+
+		if (num_clusters > vcn) {
 			/*
-			 * If there is a difference between the highest_vcn and
-			 * the highest cluster, the runlist is either corrupt
-			 * or, more likely, there are more extents following
-			 * this one.
+			 * The runlist doesn't cover all the clusters, so there
+			 * must be more extents.
 			 */
-			if (deltaxcn < max_cluster) {
-				ntfs_log_debug("More extents to follow; deltaxcn = "
-						"0x%llx, max_cluster = 0x%llx\n",
-						(long long)deltaxcn,
-						(long long)max_cluster);
-				rl[rlpos].vcn = vcn;
-				vcn += rl[rlpos].length = max_cluster - deltaxcn;
-				rl[rlpos].lcn = (LCN)LCN_RL_NOT_MAPPED;
-				rlpos++;
-			} else if (deltaxcn > max_cluster) {
-				ntfs_log_debug("Corrupt attribute. deltaxcn = "
-						"0x%llx, max_cluster = 0x%llx\n",
-						(long long)deltaxcn,
-						(long long)max_cluster);
-				goto mpa_err;
-			}
+			ntfs_log_debug("More extents to follow; vcn = 0x%llx, "
+				       "num_clusters = 0x%llx\n",
+					(long long)vcn,
+					(long long)num_clusters);
+			rl[rlpos].vcn = vcn;
+			vcn += rl[rlpos].length = num_clusters - vcn;
+			rl[rlpos].lcn = (LCN)LCN_RL_NOT_MAPPED;
+			rlpos++;
+		} else if (vcn > num_clusters) {
+			/*
+			 * There are more VCNs in the runlist than expected, so
+			 * the runlist is corrupt.
+			 */
+			ntfs_log_error("Corrupt attribute. vcn = 0x%llx, "
+				       "num_clusters = 0x%llx\n",
+					(long long)vcn,
+					(long long)num_clusters);
+			goto mpa_err;
 		}
 		rl[rlpos].lcn = (LCN)LCN_ENOENT;
 	} else /* Not the base extent. There may be more extents to follow. */