diff --git a/.travis.yml b/.travis.yml
index ea14a1846..0eb20f07c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,10 +1,12 @@
 language: csharp
 solution: ./hypar.sln
-dist: trusty
+dist: xenial
 mono: none
-dotnet: 2.1.502
+dotnet: 3.1
+install:
+  - dotnet restore
 script:
-  - dotnet build ./Elements.sln
+  - dotnet build ./Elements.sln --framework=netcoreapp3.1
   - dotnet test ./test/Elements.Tests/Elements.Tests.csproj
 env:
   - TRAVIS=true
\ No newline at end of file
diff --git a/src/Elements/Elements.csproj b/src/Elements/Elements.csproj
index 9b0f2ca95..3fc1c0b2a 100644
--- a/src/Elements/Elements.csproj
+++ b/src/Elements/Elements.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>netstandard2.0;net472;netcoreapp2.1;netcoreapp3.1</TargetFrameworks>
     <AssemblyName>Hypar.Elements</AssemblyName>
     <PackageTitle>Hypar Elements</PackageTitle>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
diff --git a/src/Elements/Serialization/IFC/IFCElementExtensions.cs b/src/Elements/Serialization/IFC/IFCElementExtensions.cs
index 4bcdc3661..7b98a1294 100644
--- a/src/Elements/Serialization/IFC/IFCElementExtensions.cs
+++ b/src/Elements/Serialization/IFC/IFCElementExtensions.cs
@@ -24,7 +24,7 @@ internal static List<IfcProduct> ToIfcProducts(this Element e,
             IfcProductDefinitionShape shape = null;
             GeometricElement geoElement = null;
             Transform trans = null;
-            Guid id;
+            Guid id = default(Guid);
 
             if (e is ElementInstance)
             {
diff --git a/test/Elements.Tests/Elements.Tests.csproj b/test/Elements.Tests/Elements.Tests.csproj
index d12fc02b1..487f12db9 100644
--- a/test/Elements.Tests/Elements.Tests.csproj
+++ b/test/Elements.Tests/Elements.Tests.csproj
@@ -1,8 +1,8 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <AssemblyName>Hypar.Elements.Tests</AssemblyName>
-    <TargetFramework>netcoreapp2.1</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
     <RootNamespace>Elements</RootNamespace>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
@@ -15,7 +15,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <ProjectReference Include="..\..\src\Elements\Elements.csproj" />
+    <ProjectReference Properties="TargetFramework=netstandard2.0" Include="..\..\src\Elements\Elements.csproj" />
   </ItemGroup>
 
   <ItemGroup>