diff --git a/NEWS b/NEWS
index 9dc0441c..729a225b 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,8 @@
 xbps-0.40 (???):
 
+ * xbps-install(8): handle xbps_transaction_prepare() returning ENOSPC, to
+   abort a transaction when there's insufficient disk space on rootdir.
+
  * xbps-query(8): -S/--show mode no longer prints ANSI escape codes if stdout
    is not a tty; suggested by @chneukirchen.
 
diff --git a/bin/xbps-install/transaction.c b/bin/xbps-install/transaction.c
index 8a9a3441..efd964a2 100644
--- a/bin/xbps-install/transaction.c
+++ b/bin/xbps-install/transaction.c
@@ -322,6 +322,9 @@ exec_transaction(struct xbps_handle *xhp, int maxcols, bool yes, bool drun)
 			array = xbps_dictionary_get(xhp->transd, "conflicts");
 			print_array(array);
 			fprintf(stderr, "Transaction aborted due to conflicting packages.\n");
+		} else if (rv == ENOSPC) {
+			/* not enough free space */
+			fprintf(stderr, "Transaction aborted due to insufficient disk space.\n");
 		} else {
 			xbps_dbg_printf(xhp, "Empty transaction dictionary: %s\n",
 			    strerror(errno));
diff --git a/lib/transaction_dictionary.c b/lib/transaction_dictionary.c
index e8157cb2..9abcc81a 100644
--- a/lib/transaction_dictionary.c
+++ b/lib/transaction_dictionary.c
@@ -173,7 +173,7 @@ compute_transaction_stats(struct xbps_handle *xhp)
 		return 0;
 	}
 	/* compute free space on disk */
-	rootdir_free_size = svfs.f_bavail * svfs.f_bsize - instsize;
+	rootdir_free_size = svfs.f_bfree * svfs.f_bsize;
 
 	if (!xbps_dictionary_set_uint64(xhp->transd,
 				"disk-free-size", rootdir_free_size))