diff --git a/src/storage/filesystem.js b/src/storage/filesystem.js
index 891ee977d..4f4592f46 100644
--- a/src/storage/filesystem.js
+++ b/src/storage/filesystem.js
@@ -54,13 +54,6 @@ function checkPreconditions(apiConfig, dataLayout, callback) {
     assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
     assert.strictEqual(typeof callback, 'function');
 
-    // Check filesystem is mounted so we don't write into the actual folder on disk
-    if (apiConfig.provider === PROVIDER_SSHFS || apiConfig.provider === PROVIDER_CIFS || apiConfig.provider === PROVIDER_NFS) {
-        const mounts = safe.fs.readFileSync('/proc/mounts', 'utf8');
-        const mountInfo = mounts.split('\n').filter(function (l) { return l.indexOf(apiConfig.mountPoint) !== -1; })[0];
-        if (!mountInfo) return callback(new BoxError(BoxError.FS_ERROR, `${apiConfig.mountPoint} is not mounted`));
-    }
-
     let used = 0;
     for (let localPath of dataLayout.localPaths()) {
         debug(`checkPreconditions: getting disk usage of ${localPath}`);
@@ -71,9 +64,17 @@ function checkPreconditions(apiConfig, dataLayout, callback) {
 
     debug(`checkPreconditions: ${used} bytes`);
 
-    df.file(getBackupPath(apiConfig)).then(function (diskUsage) {
+    df.file(getBackupPath(apiConfig)).then(function (result) {
+
+        // Check filesystem is mounted so we don't write into the actual folder on disk
+        if (apiConfig.provider === PROVIDER_SSHFS || apiConfig.provider === PROVIDER_CIFS || apiConfig.provider === PROVIDER_NFS) {
+            if (result.mountpoint !== apiConfig.mountPoint) return callback(new BoxError(BoxError.FS_ERROR, `${apiConfig.mountPoint} is not mounted`));
+        } else if (apiConfig.provider === PROVIDER_FILESYSTEM && apiConfig.externalDisk) {
+            if (result.mountpoint === '/') return callback(new BoxError(BoxError.FS_ERROR, `${apiConfig.backupFolder} is not mounted`));
+        }
+
         const needed = used + (1024 * 1024 * 1024); // check if there is atleast 1GB left afterwards
-        if (diskUsage.available <= needed) return callback(new BoxError(BoxError.FS_ERROR, `Not enough disk space for backup. Needed: ${prettyBytes(needed)} Available: ${prettyBytes(diskUsage.available)}`));
+        if (result.available <= needed) return callback(new BoxError(BoxError.FS_ERROR, `Not enough disk space for backup. Needed: ${prettyBytes(needed)} Available: ${prettyBytes(result.available)}`));
 
         callback(null);
     }).catch(function (error) {
@@ -239,7 +240,7 @@ function testConfig(apiConfig, callback) {
 
         const mounts = safe.fs.readFileSync('/proc/mounts', 'utf8');
         const mountInfo = mounts.split('\n').filter(function (l) { return l.indexOf(apiConfig.mountPoint) !== -1; })[0];
-        if (!mountInfo) return callback(new BoxError(BoxError.BAD_FIELD, 'mountPoint is not mounted', { field: 'mountPoint' }));
+        if (!mountInfo) return callback(new BoxError(BoxError.BAD_FIELD, `${apiConfig.mountPoint} is not mounted`, { field: 'mountPoint' }));
 
         if (apiConfig.provider === PROVIDER_SSHFS && !mountInfo.split(' ').find(i => i === 'fuse.sshfs')) return callback(new BoxError(BoxError.BAD_FIELD, 'mountPoint must be a "fuse.sshfs" filesystem', { field: 'mountPoint' }));
         if (apiConfig.provider === PROVIDER_CIFS && !mountInfo.split(' ').find(i => i === 'cifs')) return callback(new BoxError(BoxError.BAD_FIELD, 'mountPoint must be a "cifs" filesystem', { field: 'mountPoint' }));