How to fix Error 2740 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 2740 – Invalid Language Name

Why This Error Happens

This error occurs when the SET LANGUAGE statement references a language name or alias that does not exist in the sys.syslanguages (or sys.languages) catalog view on the target SQL Server 2025 instance. This commonly happens after a migration or restore from an older server where custom languages were installed but not replicated, or due to a typo/case-sensitivity mismatch in the language string passed by the application. It can also occur if the master database’s language catalog has been corrupted or partially rolled back during a failed service pack or cumulative update installation.

Step-by-Step Resolution Guide

Step 1: Verify the Exact Language Name on the Instance

  • Open SQL Server Management Studio (SSMS) or Azure Data Studio and connect to the SQL Server 2025 instance.
  • Run the following query to list all valid languages and their aliases:
SELECT langid, name, alias FROM sys.syslanguages;
  • Compare the output against the exact string being passed in your application’s connection string or SET LANGUAGE call (check for extra spaces, incorrect casing, or regional variants like “British” vs “British English”).

Step 2: Check the Default Language Setting at the Login/Server Level

  • Navigate to SSMS > Security > Logins > [Your Login] > Properties > General tab and verify the “Default language” dropdown matches a valid entry.
  • Alternatively, query the login configuration directly:
SELECT name, language FROM sys.server_principals WHERE name = 'YourLoginName';
  • If the login is pointing to a language not present in Step 1’s list, update it using ALTER LOGIN [YourLoginName] WITH DEFAULT_LANGUAGE = us_english;

Step 3: Reinstall or Repair Missing Language Resources

  • If a custom or regional language is missing entirely (common after an in-place upgrade on Windows Server 2025), locate the SQL Server installation media and verify the Resources\1033 (or relevant locale ID) folder under C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Binn\Resources\ is fully populated.
  • Run the SQL Server Setup in Repair mode via Control Panel > Programs > Microsoft SQL Server 2025 > Change/Repair to restore corrupted language resource files.
  • Restart the SQL Server service via services.msc or net stop MSSQLSERVER && net start MSSQLSERVER after the repair completes.

Step 4: Update the Application Connection String or Session Setting

  • If the issue originates from the application layer (e.g., an ADO.NET or ODBC connection string specifying Language=Deutsch), correct the parameter to match a confirmed valid alias from the sys.syslanguages output.
  • Redeploy or restart the application pool/service in IIS (if applicable) to ensure the corrected connection string is loaded.

Alternative or Verification Steps

  • Verify the fix by manually executing SET LANGUAGE 'us_english'; (or your corrected language) in a new query window—if no error returns, the catalog and permissions are correctly aligned.
  • As an alternative, if custom languages are not business-critical, standardize all logins and applications to use us_english as the default via sp_configure or login property changes to avoid future dependency on regional language packs.