# Warning: Could not load file or assembly WindowsBase, Version=4.0.0.0 **URL:** \ **Category:** Support\ **Created:** [January 31, 2020, 9:35am UTC](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023 "2020-01-31T09:35:04Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![sync2019](https://forum.duplicati.com/letter_avatar_proxy/v4/letter/s/f6c823/32.png) [@sync2019](https://forum.duplicati.com/u/sync2019)\ **Post date:** [January 31, 2020, 9:35am UTC](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023/1 "2020-01-31T09:35:05Z")
Hi, on ubuntu 16.04, with libmono 6.8.0.96-0xamarin4+ubuntu1604b1 and the latest Duplicati beta, I get this warning, only on one of two backup jobs: > LimitedWarnings: [2020-01-31 10:10:00 +01 - [Warning-Duplicati.Library.DynamicLoader.DynamicLoader`1-SoftError]: Impossibile caricare processo tipo System.Reactive.Concurrency.DispatcherScheduler assembly /usr/share/Duplicati/updates/2.0.5.1/System.Reactive.dll, messaggio di errore: Could not load type of field ‘System.Reactive.Concurrency.DispatcherScheduler:k\_\_BackingField’ (0) due to: Could not load file or assembly ‘WindowsBase, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35’ or one of its dependencies.] Do I need to get worried? Thanks ---
**Author:** ![ts678](https://forum.duplicati.com/letter_avatar_proxy/v4/letter/t/8491ac/32.png) [@ts678](https://forum.duplicati.com/u/ts678)\ **Post date:** [February 2, 2020, 11:18pm UTC](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023/2 "2020-02-02T23:18:16Z")
> [@sync2019](#): > > Could not load file or assembly ‘WindowsBase, Version=4.0.0.0 [Error when launching server](https://tshock.co/xf/index.php?threads/error-when-launching-server.5039/) solved this by installing mono-complete. Which mono package do you run? [Prerequisites](https://duplicati.readthedocs.io/en/latest/02-installation/#prerequisites) suggests mono-devel, but it’s possible that it’s not enough. Still, I think yours is first report. Is this two jobs on the same system with the same destination type, and are any of them an S3 backup? System.Reactive came in with S3 MinIO, but I’m not sure which of your warning lines was the initial one. ---
**Author:** ![sync2019](https://forum.duplicati.com/letter_avatar_proxy/v4/letter/s/f6c823/32.png) [@sync2019](https://forum.duplicati.com/u/sync2019)\ **Post date:** [February 3, 2020, 9:52am UTC](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023/3 "2020-02-03T09:52:10Z")
Thanks for responding. Both the jobs are on the same Ubuntu system, with the same mono installation, and connecting to Wasabi S3. Today, however, the warning has not appeared, even though I have not installed mono-complete. The only packet that was updated after the previous warning was firefox. Anyway, if the warning pops up again I will dig more the issue. ---
**Author:** ![kinghat](https://forum.duplicati.com/user_avatar/forum.duplicati.com/kinghat/32/5111_2.png) [@kinghat](https://forum.duplicati.com/u/kinghat)\ **Post date:** [February 9, 2020, 10:33pm UTC](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023/4 "2020-02-09T22:33:43Z")
ive been getting the same since updating to the newest beta after it was released: > 2020-02-09 03:00:00 -06 - [Warning-Duplicati.Library.DynamicLoader.DynamicLoader`1-SoftError]: Failed to load process type System.Reactive.Concurrency.DispatcherScheduler assembly /usr/share/Duplicati/updates/2.0.5.1/System.Reactive.dll, error message: Could not load type of field ‘System.Reactive.Concurrency.DispatcherScheduler:k\_\_BackingField’ (0) due to: Could not load file or assembly ‘WindowsBase, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35’ or one of its dependencies. > [@Warning: Could not load file or assembly WindowsBase, Version=4.0.0.0](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023/2): > > [Error when launching server](https://tshock.co/xf/index.php?threads/error-when-launching-server.5039/) solved this by installing mono-complete. Which mono package do you run? [Prerequisites](https://duplicati.readthedocs.io/en/latest/02-installation/#prerequisites) suggests mono-devel, but it’s possible that it’s not enough. Still, I think yours is first report. Is this two jobs on the same system with the same destination type, and are any of them an S3 backup? System.Reactive came in with S3 MinIO, but I’m not sure which of your warning lines was the initial one. i cant remember if i installed mono-complete or mono-devel but my mono install is: > Mono JIT compiler version 6.8.0.105 (tarball Tue Feb 4 21:20:20 UTC 2020) > Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. [www.mono-project.com](http://www.mono-project.com) > TLS: \_\_thread > SIGSEGV: altstack > Notifications: epoll > Architecture: amd64 > Disabled: none > Misc: softdebug > Interpreter: yes > LLVM: yes(610) > Suspend: hybrid > GC: sgen (concurrent by default) it doesnt happen every time my backup is ran but like every other time: ![image](https://forum.duplicati.com/uploads/default/original/2X/3/367c586eed4a7cc3786625253869c0e42768d7bb.png) ---
**Author:** ![sync2019](https://forum.duplicati.com/letter_avatar_proxy/v4/letter/s/f6c823/32.png) [@sync2019](https://forum.duplicati.com/u/sync2019)\ **Post date:** [February 10, 2020, 9:26am UTC](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023/5 "2020-02-10T09:26:59Z")
The warning appeared again on only one of my two backup jobs. So indeed it is not easy to reproduce. I also have Mono JIT compiler version 6.8.0.105. ---
**Author:** ![Arnaud](https://forum.duplicati.com/user_avatar/forum.duplicati.com/arnaud/32/2211_2.png) [@Arnaud](https://forum.duplicati.com/u/Arnaud)\ **Post date:** [February 11, 2020, 4:04pm UTC](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023/6 "2020-02-11T16:04:15Z")
I’m getting these same errors also, Ubuntu 19.10 64bit intel with 2.0.5.1\_beta\_2020-01-18. I just installed mono-complete (must have had -devel before) and will see if that fixes it. Only every 2-4 backups contains the warning, which is pretty bizarre. ``` 2020-02-11 02:00:00 -05 - [Warning-Duplicati.Library.DynamicLoader.DynamicLoader`1-SoftError]: Failed to load process type System.Reactive.Concurrency.DispatcherScheduler assembly /usr/share/Duplicati/updates/2.0.5.1/System.Reactive.dll, error message: Could not load type of field 'System.Reactive.Concurrency.DispatcherScheduler:k__BackingField' (0) due to: Could not load file or assembly 'WindowsBase, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. ``` ---
**Author:** ![sync2019](https://forum.duplicati.com/letter_avatar_proxy/v4/letter/s/f6c823/32.png) [@sync2019](https://forum.duplicati.com/u/sync2019)\ **Post date:** [February 18, 2020, 9:24am UTC](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023/7 "2020-02-18T09:24:16Z")
Has mono-complete solved the problem? I would prefer not to install a lot of new libraries just for eliminating a warning, also considering that I was able to correctly restore files from the job that raised the warning. ---
**Author:** ![sync2019](https://forum.duplicati.com/letter_avatar_proxy/v4/letter/s/f6c823/32.png) [@sync2019](https://forum.duplicati.com/u/sync2019)\ **Post date:** [February 18, 2020, 3:30pm UTC](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023/8 "2020-02-18T15:30:17Z")
[This page](https://stackoverflow.com/questions/17648647/could-not-load-file-or-assembly-system-version-4-0-0-0-culture-neutral-publi) hints at some problem when there are multiple copies of the library. On my ubuntu installation I found Duplicati both in /usr/share/Duplicati and in /home/$USER/.config/Duplicati . I do not know why. Since the files in my home folder are much older and not updated, I temporarily removed the /home/$USER/.config/Duplicati folder. I rerun the job and it has not raised the warning. Let’s see how it behaves next time. ---
**Author:** ![Arnaud](https://forum.duplicati.com/user_avatar/forum.duplicati.com/arnaud/32/2211_2.png) [@Arnaud](https://forum.duplicati.com/u/Arnaud)\ **Post date:** [February 18, 2020, 3:52pm UTC](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023/9 "2020-02-18T15:52:42Z")
Yes, it looks like that fixed it. No errors since then and it’s been a week. ---
**Author:** ![sync2019](https://forum.duplicati.com/letter_avatar_proxy/v4/letter/s/f6c823/32.png) [@sync2019](https://forum.duplicati.com/u/sync2019)\ **Post date:** [February 19, 2020, 9:13am UTC](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023/10 "2020-02-19T09:13:28Z")
Thanks. Regarding me removing the $HOME Duplicati folder, it was useless. The problem is here again. So apparently installing mono-complete is the only solution. ---
**Author:** ![Marc\_Neiger](https://forum.duplicati.com/user_avatar/forum.duplicati.com/marc_neiger/32/567_2.png) [@Marc\_Neiger](https://forum.duplicati.com/u/Marc_Neiger)\ **Post date:** [May 30, 2020, 5:03pm UTC](https://forum.duplicati.com/t/warning-could-not-load-file-or-assembly-windowsbase-version-4-0-0-0/9023/11 "2020-05-30T17:03:18Z")
OS: Debian 10 Since a few weeks, I used to have the same warning on a specific set and not the others on the very same machine, and despite options being the same across the backup sets. Installing mono-complete solved the issue, but this seems like using a sledgehammer to open a chestnut.