diff --git a/src/backuptask.js b/src/backuptask.js
index f4d974061..4aed92807 100644
--- a/src/backuptask.js
+++ b/src/backuptask.js
@@ -47,16 +47,6 @@ function canBackupApp(app) {
             app.installationState === apps.ISTATE_PENDING_UPDATE; // called from apptask
 }
 
-// binary units (non SI) 1024 based
-function prettyBytes(bytes) {
-    assert.strictEqual(typeof bytes, 'number');
-
-    const i = Math.floor(Math.log(bytes) / Math.log(1024)),
-        sizes = ['B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'];
-
-    return (bytes / Math.pow(1024, i)).toFixed(2) * 1 + '' + sizes[i];
-}
-
 async function checkPreconditions(backupConfig, dataLayout) {
     assert.strictEqual(typeof backupConfig, 'object');
     assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
@@ -79,7 +69,7 @@ async function checkPreconditions(backupConfig, dataLayout) {
     debug(`checkPreconditions: total required =${used} available=${df.available}`);
 
     const needed = 0.6 * used + (1024 * 1024 * 1024); // check if there is atleast 1GB left afterwards. aim for 60% because rsync/tgz won't need full 100%
-    if (df.available <= needed) throw new BoxError(BoxError.FS_ERROR, `Not enough disk space for backup. Needed: ${prettyBytes(needed)} Available: ${prettyBytes(df.available)}`);
+    if (df.available <= needed) throw new BoxError(BoxError.FS_ERROR, `Not enough disk space for backup. Needed: ${df.prettyBytes(needed)} Available: ${df.prettyBytes(df.available)}`);
 }
 
 // this function is called via backupupload (since it needs root to traverse app's directory)
diff --git a/src/df.js b/src/df.js
index 4c4228d78..0e19ea8be 100644
--- a/src/df.js
+++ b/src/df.js
@@ -2,13 +2,24 @@
 
 exports = module.exports = {
     disks,
-    file
+    file,
+    prettyBytes
 };
 
 const assert = require('assert'),
     BoxError = require('./boxerror.js'),
     safe = require('safetydance');
 
+// binary units (non SI) 1024 based
+function prettyBytes(bytes) {
+    assert.strictEqual(typeof bytes, 'number');
+
+    const i = Math.floor(Math.log(bytes) / Math.log(1024)),
+        sizes = ['B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'];
+
+    return (bytes / Math.pow(1024, i)).toFixed(2) * 1 + '' + sizes[i];
+}
+
 function parseLine(line) {
     const parts = line.split(/\s+/, 7); // this way the mountpoint can have spaces in it
 
diff --git a/src/updater.js b/src/updater.js
index 8904fa300..95a244f1a 100644
--- a/src/updater.js
+++ b/src/updater.js
@@ -127,7 +127,7 @@ async function checkFreeDiskSpace(neededSpace) {
     const [error, diskUsage] = await safe(df.file('/'));
     if (error) throw new BoxError(BoxError.FS_ERROR, error);
 
-    if (diskUsage.available < neededSpace) throw new BoxError(BoxError.FS_ERROR, 'Not enough disk space');
+    if (diskUsage.available < neededSpace) throw new BoxError(BoxError.FS_ERROR, `Not enough disk space. Updates require at least 2GB of free space. Available: ${df.prettyBytes(diskUsage.available)}`);
 }
 
 async function update(boxUpdateInfo, options, progressCallback) {