Method 'Finalise' in type 'Glass.Mapper.Sc.IoC.DependencyResolver' ... does not have an implementation

We were on 8.2.3 and I am trying to get our instance up to 9.3. I started with a vanilla 9.3 initial install and installed an update to apply our custom renderings, templates, etc. At the end of the installation I got the error below:

Method ‘Finalise’ in type ‘Glass.Mapper.Sc.IoC.DependencyResolver’ from assembly ‘Glass.Mapper.Sc, Version=4.3.4.197, Culture=neutral, PublicKeyToken=null’ does not have an implementation.

Description: An
unhandled exception occurred during the execution of the current web
request. Please review the stack trace for more information about the
error and where it originated in the code.

Exception Details: System.TypeLoadException: Method ‘Finalise’ in type
‘Glass.Mapper.Sc.IoC.DependencyResolver’ from assembly
‘Glass.Mapper.Sc, Version=4.3.4.197, Culture=neutral,
PublicKeyToken=null’ does not have an implementation.

Source Error:

An unhandled exception was generated during the execution of the
current web request. Information regarding the origin and location of
the exception can be identified using the exception stack trace below.

Stack Trace:

[TypeLoadException: Method ‘Finalise’ in type
‘Glass.Mapper.Sc.IoC.DependencyResolver’ from assembly
‘Glass.Mapper.Sc, Version=4.3.4.197, Culture=neutral,
PublicKeyToken=null’ does not have an implementation.]
Dkg.Web.App_Start.GlassMapperScCustom.CreateResolver() +0
Dkg.Web.App_Start.GlassMapperSc.Start() +11 (Object , Object ) +9
Sitecore.Pipelines.CorePipeline.Run(PipelineArgs args) +484
Sitecore.Pipelines.DefaultCorePipelineManager.Run(String pipelineName,
PipelineArgs args, String pipelineDomain, Boolean failIfNotExists)
+236 Sitecore.Pipelines.DefaultCorePipelineManager.Run(String pipelineName, PipelineArgs args, String pipelineDomain) +22
Sitecore.Nexus.Web.HttpModule.Application_Start() +220
Sitecore.Nexus.Web.HttpModule.Init(HttpApplication app) +1145
System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr
appContext, HttpContext context, MethodInfo[] handlers) +580
System.Web.HttpApplication.InitSpecial(HttpApplicationState state,
MethodInfo[] handlers, IntPtr appContext, HttpContext context) +165
System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr
appContext, HttpContext context) +267
System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr
appContext) +341

[HttpException (0x80004005): Method ‘Finalise’ in type
‘Glass.Mapper.Sc.IoC.DependencyResolver’ from assembly
‘Glass.Mapper.Sc, Version=4.3.4.197, Culture=neutral,
PublicKeyToken=null’ does not have an implementation.]
System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +523
System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context)
+107 System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest
wr, HttpContext context) +688