diff --git a/.paket/Paket.Restore.targets b/.paket/Paket.Restore.targets
index 818b4eca..a7955581 100644
--- a/.paket/Paket.Restore.targets
+++ b/.paket/Paket.Restore.targets
@@ -5,6 +5,11 @@
     <!-- make MSBuild track this file for incremental builds. -->
     <!-- ref https://blogs.msdn.microsoft.com/msbuild/2005/09/26/how-to-ensure-changes-to-a-custom-target-file-prompt-a-rebuild/ -->
     <MSBuildAllProjects>$(MSBuildAllProjects);$(MSBuildThisFileFullPath)</MSBuildAllProjects>
+
+    <DetectedMSBuildVersion>$(MSBuildVersion)</DetectedMSBuildVersion>
+    <DetectedMSBuildVersion Condition="'$(MSBuildVersion)' == ''">15.0.0</DetectedMSBuildVersion>
+    <MSBuildSupportsHashing>false</MSBuildSupportsHashing>
+    <MSBuildSupportsHashing Condition=" '$(DetectedMSBuildVersion)' &gt; '15.8.0' ">true</MSBuildSupportsHashing>
     <!-- Mark that this target file has been loaded.  -->
     <IsPaketRestoreTargetsFileLoaded>true</IsPaketRestoreTargetsFileLoaded>
     <PaketToolsPath>$(MSBuildThisFileDirectory)</PaketToolsPath>
@@ -22,44 +27,13 @@
     <PaketBootStrapperExePath Condition=" '$(PaketBootStrapperExePath)' == '' AND Exists('$(PaketRootPath)paket.bootstrapper.exe')">$(PaketRootPath)paket.bootstrapper.exe</PaketBootStrapperExePath>
     <PaketBootStrapperExePath Condition=" '$(PaketBootStrapperExePath)' == '' ">$(PaketToolsPath)paket.bootstrapper.exe</PaketBootStrapperExePath>
     <PaketBootStrapperExeDir Condition=" Exists('$(PaketBootStrapperExePath)') " >$([System.IO.Path]::GetDirectoryName("$(PaketBootStrapperExePath)"))\</PaketBootStrapperExeDir>
-
-    <!-- Paket -->
-
-    <!-- windows, root => tool => proj style => bootstrapper => global -->
-    <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' == 'Windows_NT' AND Exists('$(PaketRootPath)paket.exe') ">$(PaketRootPath)paket.exe</PaketExePath>
-    <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' == 'Windows_NT' AND Exists('$(PaketToolsPath)paket.exe') ">$(PaketToolsPath)paket.exe</PaketExePath>
-    <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' == 'Windows_NT' AND '$(PaketBootstrapperStyle)' == 'proj' ">$(PaketToolsPath)paket.exe</PaketExePath>
-    <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' == 'Windows_NT' AND Exists('$(PaketBootStrapperExeDir)') ">$(_PaketBootStrapperExeDir)paket.exe</PaketExePath>
-    <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' == 'Windows_NT' ">paket.exe</PaketExePath>
-
-    <!-- no windows, try native paket as default,  root => tool => proj style => mono paket => bootstrpper => global -->
-    <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' AND Exists('$(PaketRootPath)paket') ">$(PaketRootPath)paket</PaketExePath>
-    <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' AND Exists('$(PaketToolsPath)paket') ">$(PaketToolsPath)paket</PaketExePath>
-    <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' AND '$(PaketBootstrapperStyle)' == 'proj' ">$(PaketToolsPath)paket</PaketExePath>
-
-    <!-- no windows, try mono paket -->
-    <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' AND Exists('$(PaketRootPath)paket.exe') ">$(PaketRootPath)paket.exe</PaketExePath>
-    <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' AND Exists('$(PaketToolsPath)paket.exe') ">$(PaketToolsPath)paket.exe</PaketExePath>
-
-    <!-- no windows, try bootstrapper -->
-    <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' AND Exists('$(PaketBootStrapperExeDir)') ">$(PaketBootStrapperExeDir)paket.exe</PaketExePath>
-
-    <!-- no windows, try global native paket -->
-    <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' ">paket</PaketExePath>
-
-    <!-- Paket command -->
-    <_PaketExeExtension>$([System.IO.Path]::GetExtension("$(PaketExePath)"))</_PaketExeExtension>
-    <PaketCommand Condition=" '$(PaketCommand)' == '' AND '$(_PaketExeExtension)' == '.dll' ">dotnet "$(PaketExePath)"</PaketCommand>
-    <PaketCommand Condition=" '$(PaketCommand)' == '' AND '$(OS)' != 'Windows_NT' AND '$(_PaketExeExtension)' == '.exe' ">$(MonoPath) --runtime=v4.0.30319 "$(PaketExePath)"</PaketCommand>
-    <PaketCommand Condition=" '$(PaketCommand)' == '' ">"$(PaketExePath)"</PaketCommand>
-
-
+    
     <PaketBootStrapperCommand Condition=" '$(OS)' == 'Windows_NT'">"$(PaketBootStrapperExePath)"</PaketBootStrapperCommand>
     <PaketBootStrapperCommand Condition=" '$(OS)' != 'Windows_NT' ">$(MonoPath) --runtime=v4.0.30319 "$(PaketBootStrapperExePath)"</PaketBootStrapperCommand>
 
     <!-- Disable automagic references for F# dotnet sdk -->
     <!-- This will not do anything for other project types -->
-    <!-- see https://github.com/fsharp/fslang-design/blob/master/RFCs/FS-1032-fsharp-in-dotnet-sdk.md -->
+    <!-- see https://github.com/fsharp/fslang-design/blob/master/tooling/FST-1002-fsharp-in-dotnet-sdk.md -->
     <DisableImplicitFSharpCoreReference>true</DisableImplicitFSharpCoreReference>
     <DisableImplicitSystemValueTupleReference>true</DisableImplicitSystemValueTupleReference>
 
@@ -69,41 +43,102 @@
     <PaketIntermediateOutputPath Condition=" '$(PaketIntermediateOutputPath)' == '' ">$(BaseIntermediateOutputPath.TrimEnd('\').TrimEnd('\/'))</PaketIntermediateOutputPath>
   </PropertyGroup>
 
+  <!-- Check if paket is available as local dotnet cli tool -->
+  <Target Name="SetPaketCommand" >
+  
+    <!-- Call 'dotnet paket' and see if it returns without an error. Mute all the output. -->
+    <Exec Command="dotnet paket --version" IgnoreExitCode="true" StandardOutputImportance="low" StandardErrorImportance="low" >
+      <Output TaskParameter="ExitCode" PropertyName="LocalPaketToolExitCode" />
+    </Exec>
+
+    <!-- If local paket tool is found, use that -->
+    <PropertyGroup Condition=" '$(LocalPaketToolExitCode)' == '0' ">
+      <InternalPaketCommand>dotnet paket</InternalPaketCommand>
+    </PropertyGroup>
+
+    <!-- If not, then we go through our normal steps of setting the Paket command.  -->
+    <PropertyGroup Condition=" '$(LocalPaketToolExitCode)' != '0' ">
+      <!-- windows, root => tool => proj style => bootstrapper => global -->
+      <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' == 'Windows_NT' AND Exists('$(PaketRootPath)paket.exe') ">$(PaketRootPath)paket.exe</PaketExePath>
+      <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' == 'Windows_NT' AND Exists('$(PaketToolsPath)paket.exe') ">$(PaketToolsPath)paket.exe</PaketExePath>
+      <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' == 'Windows_NT' AND '$(PaketBootstrapperStyle)' == 'proj' ">$(PaketToolsPath)paket.exe</PaketExePath>
+      <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' == 'Windows_NT' AND Exists('$(PaketBootStrapperExeDir)') ">$(_PaketBootStrapperExeDir)paket.exe</PaketExePath>
+      <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' == 'Windows_NT' ">paket.exe</PaketExePath>
+
+      <!-- no windows, try native paket as default,  root => tool => proj style => mono paket => bootstrpper => global -->
+      <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' AND Exists('$(PaketRootPath)paket') ">$(PaketRootPath)paket</PaketExePath>
+      <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' AND Exists('$(PaketToolsPath)paket') ">$(PaketToolsPath)paket</PaketExePath>
+      <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' AND '$(PaketBootstrapperStyle)' == 'proj' ">$(PaketToolsPath)paket</PaketExePath>
+
+      <!-- no windows, try mono paket -->
+      <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' AND Exists('$(PaketRootPath)paket.exe') ">$(PaketRootPath)paket.exe</PaketExePath>
+      <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' AND Exists('$(PaketToolsPath)paket.exe') ">$(PaketToolsPath)paket.exe</PaketExePath>
+
+      <!-- no windows, try bootstrapper -->
+      <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' AND Exists('$(PaketBootStrapperExeDir)') ">$(PaketBootStrapperExeDir)paket.exe</PaketExePath>
+
+      <!-- no windows, try global native paket -->
+      <PaketExePath Condition=" '$(PaketExePath)' == '' AND '$(OS)' != 'Windows_NT' ">paket</PaketExePath>
+
+      <_PaketExeExtension>$([System.IO.Path]::GetExtension("$(PaketExePath)"))</_PaketExeExtension>
+      <InternalPaketCommand Condition=" '$(InternalPaketCommand)' == '' AND '$(_PaketExeExtension)' == '.dll' ">dotnet "$(PaketExePath)"</InternalPaketCommand>
+      <InternalPaketCommand Condition=" '$(InternalPaketCommand)' == '' AND '$(OS)' != 'Windows_NT' AND '$(_PaketExeExtension)' == '.exe' ">$(MonoPath) --runtime=v4.0.30319 "$(PaketExePath)"</InternalPaketCommand>
+      <InternalPaketCommand Condition=" '$(InternalPaketCommand)' == '' ">"$(PaketExePath)"</InternalPaketCommand>
+
+    </PropertyGroup>
+
+    <!-- The way to get a property to be available outside the target is to use this task. -->
+    <CreateProperty Value="$(InternalPaketCommand)">
+      <Output TaskParameter="Value" PropertyName="PaketCommand"/>
+    </CreateProperty>
+
+  </Target>
+
   <Target Name="PaketBootstrapping" Condition="Exists('$(PaketToolsPath)paket.bootstrapper.proj')">
     <MSBuild Projects="$(PaketToolsPath)paket.bootstrapper.proj" Targets="Restore" />
   </Target>
 
-  <Target Name="PaketRestore" Condition="'$(PaketRestoreDisabled)' != 'True'" BeforeTargets="_GenerateDotnetCliToolReferenceSpecs;_GenerateProjectRestoreGraphPerFramework;_GenerateRestoreGraphWalkPerFramework;CollectPackageReferences" DependsOnTargets="PaketBootstrapping">
+  <!-- Official workaround for https://docs.microsoft.com/en-us/visualstudio/msbuild/getfilehash-task?view=vs-2019 -->
+  <UsingTask TaskName="Microsoft.Build.Tasks.GetFileHash" AssemblyName="Microsoft.Build.Tasks.Core, Version=15.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" Condition=" '$(MSBuildSupportsHashing)' == 'true' And '$(DetectedMSBuildVersion)' &lt; '16.0.360' " />
+  <UsingTask TaskName="Microsoft.Build.Tasks.VerifyFileHash" AssemblyName="Microsoft.Build.Tasks.Core, Version=15.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" Condition=" '$(MSBuildSupportsHashing)' == 'true' And '$(DetectedMSBuildVersion)' &lt; '16.0.360' " />
+  <Target Name="PaketRestore" Condition="'$(PaketRestoreDisabled)' != 'True'" BeforeTargets="_GenerateDotnetCliToolReferenceSpecs;_GenerateProjectRestoreGraphPerFramework;_GenerateRestoreGraphWalkPerFramework;CollectPackageReferences" DependsOnTargets="SetPaketCommand;PaketBootstrapping">
 
-    <!-- Step 1 Check if lockfile is properly restored -->
+    <!-- Step 1 Check if lockfile is properly restored (if the hash of the lockfile and the cache-file match) -->
     <PropertyGroup>
       <PaketRestoreRequired>true</PaketRestoreRequired>
       <NoWarn>$(NoWarn);NU1603;NU1604;NU1605;NU1608</NoWarn>
+      <CacheFilesExist>false</CacheFilesExist>
+      <CacheFilesExist Condition=" Exists('$(PaketRestoreCacheFile)') And Exists('$(PaketLockFilePath)') ">true</CacheFilesExist>
     </PropertyGroup>
 
-    <!-- Because ReadAllText is slow on osx/linux, try to find shasum and awk -->
-    <PropertyGroup>
-      <PaketRestoreCachedHasher Condition="'$(OS)' != 'Windows_NT' And '$(PaketRestoreCachedHasher)' == '' And Exists('/usr/bin/shasum') And Exists('/usr/bin/awk')">/usr/bin/shasum "$(PaketRestoreCacheFile)" | /usr/bin/awk '{ print $1 }'</PaketRestoreCachedHasher>
-      <PaketRestoreLockFileHasher Condition="'$(OS)' != 'Windows_NT' And '$(PaketRestoreLockFileHash)' == '' And Exists('/usr/bin/shasum') And Exists('/usr/bin/awk')">/usr/bin/shasum "$(PaketLockFilePath)" | /usr/bin/awk '{ print $1 }'</PaketRestoreLockFileHasher>
+    <!-- Read the hash of the lockfile -->
+    <GetFileHash Condition=" '$(MSBuildSupportsHashing)' == 'true' And '$(CacheFilesExist)' == 'true' " Files="$(PaketLockFilePath)" Algorithm="SHA256" HashEncoding="hex" >
+      <Output TaskParameter="Hash" PropertyName="PaketRestoreLockFileHash" />
+    </GetFileHash>
+    <!-- Read the hash of the cache, which is json, but a very simple key value object -->
+    <PropertyGroup Condition=" '$(MSBuildSupportsHashing)' == 'true' And '$(CacheFilesExist)' == 'true' ">
+        <PaketRestoreCachedContents>$([System.IO.File]::ReadAllText('$(PaketRestoreCacheFile)'))</PaketRestoreCachedContents>
+    </PropertyGroup>
+    <ItemGroup Condition=" '$(MSBuildSupportsHashing)' == 'true' And '$(CacheFilesExist)' == 'true' ">
+        <!-- Parse our simple 'paket.restore.cached' json ...-->
+        <PaketRestoreCachedSplitObject Include="$([System.Text.RegularExpressions.Regex]::Split(`$(PaketRestoreCachedContents)`, `{|}|,`))"></PaketRestoreCachedSplitObject>
+        <!-- Keep Key, Value ItemGroup-->
+        <PaketRestoreCachedKeyValue Include="@(PaketRestoreCachedSplitObject)" 
+            Condition=" $([System.Text.RegularExpressions.Regex]::Split(`%(Identity)`, `&quot;: &quot;`).Length) &gt; 1 ">
+          <Key>$([System.Text.RegularExpressions.Regex]::Split(`%(Identity)`, `": "`)[0].Replace(`"`, ``).Replace(` `, ``))</Key>
+          <Value>$([System.Text.RegularExpressions.Regex]::Split(`%(Identity)`, `": "`)[1].Replace(`"`, ``).Replace(` `, ``))</Value>
+        </PaketRestoreCachedKeyValue>
+    </ItemGroup>
+    <PropertyGroup Condition=" '$(MSBuildSupportsHashing)' == 'true' And '$(CacheFilesExist)' == 'true' ">
+        <!-- Retrieve the hashes we are interested in -->
+        <PackagesDownloadedHash Condition=" '%(PaketRestoreCachedKeyValue.Key)' == 'packagesDownloadedHash' ">%(PaketRestoreCachedKeyValue.Value)</PackagesDownloadedHash>
+        <ProjectsRestoredHash Condition=" '%(PaketRestoreCachedKeyValue.Key)' == 'projectsRestoredHash' ">%(PaketRestoreCachedKeyValue.Value)</ProjectsRestoredHash>
     </PropertyGroup>
 
-    <!-- If shasum and awk exist get the hashes -->
-    <Exec StandardOutputImportance="Low" Condition=" '$(PaketRestoreCachedHasher)' != '' " Command="$(PaketRestoreCachedHasher)" ConsoleToMSBuild='true'>
-      <Output TaskParameter="ConsoleOutput" PropertyName="PaketRestoreCachedHash" />
-    </Exec>
-    <Exec StandardOutputImportance="Low" Condition=" '$(PaketRestoreLockFileHasher)' != '' " Command="$(PaketRestoreLockFileHasher)" ConsoleToMSBuild='true'>
-      <Output TaskParameter="ConsoleOutput" PropertyName="PaketRestoreLockFileHash" />
-    </Exec>
-
-    <!-- Debug whats going on -->
-    <Message Importance="low" Text="calling paket restore with targetframework=$(TargetFramework) targetframeworks=$(TargetFrameworks)" />
-
-    <PropertyGroup Condition="Exists('$(PaketRestoreCacheFile)') ">
-      <!-- if no hash has been done yet fall back to just reading in the files and comparing them -->
-      <PaketRestoreCachedHash Condition=" '$(PaketRestoreCachedHash)' == '' ">$([System.IO.File]::ReadAllText('$(PaketRestoreCacheFile)'))</PaketRestoreCachedHash>
-      <PaketRestoreLockFileHash Condition=" '$(PaketRestoreLockFileHash)' == '' ">$([System.IO.File]::ReadAllText('$(PaketLockFilePath)'))</PaketRestoreLockFileHash>
+    <PropertyGroup Condition=" '$(MSBuildSupportsHashing)' == 'true' And '$(CacheFilesExist)' == 'true' ">
+      <!-- If the restore file doesn't exist we need to restore, otherwise only if hashes don't match -->
       <PaketRestoreRequired>true</PaketRestoreRequired>
-      <PaketRestoreRequired Condition=" '$(PaketRestoreLockFileHash)' == '$(PaketRestoreCachedHash)' ">false</PaketRestoreRequired>
+      <PaketRestoreRequired Condition=" '$(PaketRestoreLockFileHash)' == '$(ProjectsRestoredHash)' ">false</PaketRestoreRequired>
       <PaketRestoreRequired Condition=" '$(PaketRestoreLockFileHash)' == '' ">true</PaketRestoreRequired>
     </PropertyGroup>
 
@@ -116,7 +151,10 @@
     </PropertyGroup>
 
     <!-- Do a global restore if required -->
+    <Warning Text="This version of MSBuild (we assume '$(DetectedMSBuildVersion)' or older) doesn't support GetFileHash, so paket fast restore is disabled." Condition=" '$(MSBuildSupportsHashing)' != 'true' " />
+    <Error Text="Stop build because of PAKET_ERROR_ON_MSBUILD_EXEC and we always call the bootstrapper" Condition=" '$(PAKET_ERROR_ON_MSBUILD_EXEC)' == 'true' AND '$(PaketBootstrapperStyle)' == 'classic' AND Exists('$(PaketBootStrapperExePath)') AND !(Exists('$(PaketExePath)'))" />
     <Exec Command='$(PaketBootStrapperCommand)' Condition=" '$(PaketBootstrapperStyle)' == 'classic' AND Exists('$(PaketBootStrapperExePath)') AND !(Exists('$(PaketExePath)'))" ContinueOnError="false" />
+    <Error Text="Stop build because of PAKET_ERROR_ON_MSBUILD_EXEC and we need a full restore (hashes don't match)" Condition=" '$(PAKET_ERROR_ON_MSBUILD_EXEC)' == 'true' AND '$(PaketRestoreRequired)' == 'true' AND '$(PaketDisableGlobalRestore)' != 'true'" />
     <Exec Command='$(PaketCommand) restore' Condition=" '$(PaketRestoreRequired)' == 'true' AND '$(PaketDisableGlobalRestore)' != 'true' " ContinueOnError="false" />
     
     <!-- Step 2 Detect project specific changes -->
@@ -126,7 +164,7 @@
       <MyTargetFrameworks Condition="'$(TargetFrameworks)' != '' AND '$(TargetFramework)' == '' " Include="$(TargetFrameworks)"></MyTargetFrameworks>
       <PaketResolvedFilePaths Include="@(MyTargetFrameworks -> '$(PaketIntermediateOutputPath)\$(MSBuildProjectFile).%(Identity).paket.resolved')"></PaketResolvedFilePaths>
     </ItemGroup>
-    <Message Importance="low" Text="MyTargetFrameworks=@(MyTargetFrameworks) PaketResolvedFilePaths=@(PaketResolvedFilePaths)" />
+
     <PropertyGroup>
       <PaketReferencesCachedFilePath>$(PaketIntermediateOutputPath)\$(MSBuildProjectFile).paket.references.cached</PaketReferencesCachedFilePath>
       <!-- MyProject.fsproj.paket.references has the highest precedence -->
@@ -163,6 +201,7 @@
 
     <!-- Step 3 Restore project specific stuff if required -->
     <Message Condition=" '$(PaketRestoreRequired)' == 'true' " Importance="low" Text="Detected a change ('$(PaketRestoreRequiredReason)') in the project file '$(MSBuildProjectFullPath)', calling paket restore" />
+    <Error Text="Stop build because of PAKET_ERROR_ON_MSBUILD_EXEC and we detected a change ('$(PaketRestoreRequiredReason)') in the project file '$(MSBuildProjectFullPath)'" Condition=" '$(PAKET_ERROR_ON_MSBUILD_EXEC)' == 'true' AND '$(PaketRestoreRequired)' == 'true' " />
     <Exec Command='$(PaketCommand) restore --project "$(MSBuildProjectFullPath)" --output-path "$(PaketIntermediateOutputPath)" --target-framework "$(TargetFrameworks)"' Condition=" '$(PaketRestoreRequired)' == 'true' AND '$(TargetFramework)' == '' " ContinueOnError="false" />
     <Exec Command='$(PaketCommand) restore --project "$(MSBuildProjectFullPath)" --output-path "$(PaketIntermediateOutputPath)" --target-framework "$(TargetFramework)"' Condition=" '$(PaketRestoreRequired)' == 'true' AND '$(TargetFramework)' != '' " ContinueOnError="false" />
 
@@ -184,7 +223,7 @@
         <PackageName>$([System.String]::Copy('%(PaketReferencesFileLines.Identity)').Split(',')[0])</PackageName>
         <PackageVersion>$([System.String]::Copy('%(PaketReferencesFileLines.Identity)').Split(',')[1])</PackageVersion>
         <AllPrivateAssets>$([System.String]::Copy('%(PaketReferencesFileLines.Identity)').Split(',')[4])</AllPrivateAssets>
-        <CopyLocal Condition="'$(Splits)' == '6'">$([System.String]::Copy('%(PaketReferencesFileLines.Identity)').Split(',')[5])</CopyLocal>
+        <CopyLocal Condition="'%(PaketReferencesFileLinesInfo.Splits)' == '6'">$([System.String]::Copy('%(PaketReferencesFileLines.Identity)').Split(',')[5])</CopyLocal>
       </PaketReferencesFileLinesInfo>
       <PackageReference Include="%(PaketReferencesFileLinesInfo.PackageName)">
         <Version>%(PaketReferencesFileLinesInfo.PackageVersion)</Version>
@@ -224,12 +263,10 @@
   <Target Name="PaketDisableDirectPack" AfterTargets="_IntermediatePack" BeforeTargets="GenerateNuspec" Condition="('$(IsPackable)' == '' Or '$(IsPackable)' == 'true') And Exists('$(PaketIntermediateOutputPath)/$(MSBuildProjectFile).references')" >
     <PropertyGroup>
       <ContinuePackingAfterGeneratingNuspec>false</ContinuePackingAfterGeneratingNuspec>
-      <DetectedMSBuildVersion>$(MSBuildVersion)</DetectedMSBuildVersion>
-      <DetectedMSBuildVersion Condition="$(MSBuildVersion) == ''">15.8.0</DetectedMSBuildVersion>
     </PropertyGroup>
   </Target>
 
-  <Target Name="PaketOverrideNuspec" AfterTargets="GenerateNuspec" Condition="('$(IsPackable)' == '' Or '$(IsPackable)' == 'true') And Exists('$(PaketIntermediateOutputPath)/$(MSBuildProjectFile).references')" >
+  <Target Name="PaketOverrideNuspec" DependsOnTargets="SetPaketCommand" AfterTargets="GenerateNuspec" Condition="('$(IsPackable)' == '' Or '$(IsPackable)' == 'true') And Exists('$(PaketIntermediateOutputPath)/$(MSBuildProjectFile).references')" >
     <ItemGroup>
       <_NuspecFilesNewLocation Include="$(PaketIntermediateOutputPath)\$(Configuration)\*.nuspec"/>
       <MSBuildMajorVersion Include="$(DetectedMSBuildVersion.Replace(`-`, `.`).Split(`.`)[0])" />
@@ -252,10 +289,12 @@
     </PropertyGroup>
 
     <ItemGroup>
-      <_NuspecFiles Include="$(AdjustedNuspecOutputPath)\*.$(PackageVersion).nuspec"/>
+      <_NuspecFiles Include="$(AdjustedNuspecOutputPath)\*.$(PackageVersion.Split(`+`)[0]).nuspec"/>
     </ItemGroup>
 
-    <Exec Command='$(PaketCommand) fix-nuspecs files "@(_NuspecFiles)" project-file "$(PaketProjectFile)" ' Condition="@(_NuspecFiles) != ''" />
+    <Error Text="Error Because of PAKET_ERROR_ON_MSBUILD_EXEC (not calling fix-nuspecs)" Condition=" '$(PAKET_ERROR_ON_MSBUILD_EXEC)' == 'true' " />
+    <Exec Condition="@(_NuspecFiles) != ''" Command='$(PaketCommand) fix-nuspecs files "@(_NuspecFiles)" project-file "$(PaketProjectFile)" ' />
+    <Error Condition="@(_NuspecFiles) == ''" Text='Could not find nuspec files in "$(AdjustedNuspecOutputPath)" (Version: "$(PackageVersion)"), therefore we cannot call "paket fix-nuspecs" and have to error out!' />
 
     <ConvertToAbsolutePath Condition="@(_NuspecFiles) != ''" Paths="@(_NuspecFiles)">
       <Output TaskParameter="AbsolutePaths" PropertyName="NuspecFileAbsolutePath" />
@@ -281,7 +320,7 @@
               DevelopmentDependency="$(DevelopmentDependency)"
               BuildOutputInPackage="@(_BuildOutputInPackage)"
               TargetPathsToSymbols="@(_TargetPathsToSymbols)"
-              SymbolPackageFormat="symbols.nupkg"
+              SymbolPackageFormat="$(SymbolPackageFormat)"
               TargetFrameworks="@(_TargetFrameworks)"
               AssemblyName="$(AssemblyName)"
               PackageOutputPath="$(PackageOutputAbsolutePath)"
@@ -328,7 +367,7 @@
               DevelopmentDependency="$(DevelopmentDependency)"
               BuildOutputInPackage="@(_BuildOutputInPackage)"
               TargetPathsToSymbols="@(_TargetPathsToSymbols)"
-              SymbolPackageFormat="symbols.nupkg"
+              SymbolPackageFormat="$(SymbolPackageFormat)"
               TargetFrameworks="@(_TargetFrameworks)"
               AssemblyName="$(AssemblyName)"
               PackageOutputPath="$(PackageOutputAbsolutePath)"
diff --git a/src/Numerics/Optimization/BfgsBMinimizer.cs b/src/Numerics/Optimization/BfgsBMinimizer.cs
index a1f79d96..773f1b02 100644
--- a/src/Numerics/Optimization/BfgsBMinimizer.cs
+++ b/src/Numerics/Optimization/BfgsBMinimizer.cs
@@ -140,6 +140,7 @@ namespace MathNet.Numerics.Optimization
 
             var previousPoint = objective.Fork();
             var candidatePoint = lineSearchResult.FunctionInfoAtMinimum;
+            ValidateGradientAndObjective(candidatePoint);
 
             // Check that we're not done
             currentExitCondition = ExitCriteriaSatisfied(candidatePoint, previousPoint, 0);