I'm getting this error when upgrading from 7.5.3 to 7.5.11:

The database failed to upgrade. ERROR: The database configuration failed with the following message: An explicit DROP INDEX is not allowed on index 'umbracoNode.IXumbracoNodeUniqueID'. It is being used for FOREIGN KEY constraint enforcement. Please check log file for additional information (can be found in '/AppData/Logs/UmbracoTraceLog.txt')

Here is the log file:

2017-03-18 16:04:36,116 [P384/D5/T28] INFO  Umbraco.Core.Persistence.Migrations.MigrationRunner - Executing sql statement 1: CREATE CLUSTERED INDEX [IX_umbracoUserLogins_Index] ON [umbracoUserLogins] ([contextID])

 2017-03-18 16:04:36,163 [P384/D5/T28] INFO  Umbraco.Core.Persistence.Migrations.MigrationRunner - Executing sql statement 2: ALTER TABLE [umbracoUser] ALTER COLUMN [userPassword] NVARCHAR(500) NOT NULL

 2017-03-18 16:04:36,303 [P384/D5/T28] INFO  Umbraco.Core.Persistence.Migrations.MigrationRunner - Executing sql statement 5: ALTER TABLE [cmsContent] ADD CONSTRAINT [FK_cmsContent_cmsContentType_nodeId] FOREIGN KEY ([contentType]) REFERENCES [cmsContentType] ([nodeId])

 2017-03-18 16:04:36,334 [P384/D5/T28] INFO  Umbraco.Core.Persistence.Migrations.MigrationRunner - Executing sql statement 6: DROP INDEX [IX_umbracoNodeUniqueID] ON [umbracoNode]

 2017-03-18 16:04:36,381 [P384/D5/T28] ERROR Umbraco.Core.Persistence.UmbracoDatabase - Database exception occurred
System.Data.SqlClient.SqlException (0x80131904): An explicit DROP INDEX is not allowed on index 'umbracoNode.IX_umbracoNodeUniqueID'. It is being used for FOREIGN KEY constraint enforcement.
   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async, Int32 timeout, Boolean asyncWrite)
   at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean asyncWrite)
   at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at StackExchange.Profiling.Data.ProfiledDbCommand.ExecuteNonQuery()
   at Umbraco.Core.Persistence.PetaPocoCommandExtensions.<>c__DisplayClass1.<ExecuteNonQueryWithRetry>b__0()
   at Umbraco.Core.Persistence.FaultHandling.RetryPolicy.ExecuteAction[TResult](Func`1 func)
   at Umbraco.Core.Persistence.Database.Execute(String sql, Object[] args)
ClientConnectionId:ce6937a4-b031-4cc1-9c86-f5bdf4810912

any ideas on how to solve this?

Best regards, Vlad.