diff --git a/Speckle.InterfaceGenerator.Tests/AccessorsGenerationTests.cs b/Speckle.InterfaceGenerator.Tests/AccessorsGenerationTests.cs
index 3baf4c7..ebdeb51 100644
--- a/Speckle.InterfaceGenerator.Tests/AccessorsGenerationTests.cs
+++ b/Speckle.InterfaceGenerator.Tests/AccessorsGenerationTests.cs
@@ -166,21 +166,21 @@ internal class AccessorsTestsService : IAccessorsTestsService
         set { }
     }
 
-    public string PublicProperty { get; set; }
+    public string PublicProperty { get; set; } = string.Empty;
 
-    public string InitOnlyProperty { get; init; }
+    public string InitOnlyProperty { get; init; } = string.Empty;
 
-    public string PropertyWithPrivateSetter { get; private set; }
+    public string PropertyWithPrivateSetter { get; private set; } = string.Empty;
 
-    public string PropertyWithPrivateGetter { private get; set; }
+    public string PropertyWithPrivateGetter { private get; set; } = string.Empty;
 
-    public string PropertyWithProtectedSetter { get; protected set; }
+    public string PropertyWithProtectedSetter { get; protected set; } = string.Empty;
 
-    public string PropertyWithProtectedGetter { protected get; set; }
+    public string PropertyWithProtectedGetter { protected get; set; } = string.Empty;
 
     [AutoInterfaceIgnore]
-    public string IgnoredProperty { get; set; }
+    public string IgnoredProperty { get; set; } = string.Empty;
 
-    public static string StaticProperty { get; set; }
+    public static string StaticProperty { get; set; } = string.Empty;
 }
 // ReSharper enable UnusedMember.Local, ValueParameterNotUsed
diff --git a/Speckle.InterfaceGenerator.Tests/MethodGenerationTests.cs b/Speckle.InterfaceGenerator.Tests/MethodGenerationTests.cs
index 36ea1e7..263766b 100644
--- a/Speckle.InterfaceGenerator.Tests/MethodGenerationTests.cs
+++ b/Speckle.InterfaceGenerator.Tests/MethodGenerationTests.cs
@@ -331,7 +331,7 @@ internal class MethodsTestService : IMethodsTestService
 
     public void VoidMethodWithOutParam(out string a)
     {
-        a = default;
+        a = string.Empty;
     }
 
     public void VoidMethodWithRefParam(ref string a) { }
diff --git a/Speckle.InterfaceGenerator.Tests/Speckle.InterfaceGenerator.Tests.csproj b/Speckle.InterfaceGenerator.Tests/Speckle.InterfaceGenerator.Tests.csproj
index d3121c9..1115338 100644
--- a/Speckle.InterfaceGenerator.Tests/Speckle.InterfaceGenerator.Tests.csproj
+++ b/Speckle.InterfaceGenerator.Tests/Speckle.InterfaceGenerator.Tests.csproj
@@ -4,6 +4,8 @@
         <TargetFramework>net8.0</TargetFramework>
         <IsPackable>false</IsPackable>
         <RootNamespace>Speckle.InterfaceGenerator.Tests</RootNamespace>
+        <Nullable>enable</Nullable>
+        <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     </PropertyGroup>
 
     <ItemGroup>
diff --git a/Speckle.InterfaceGenerator/Speckle.InterfaceGenerator.csproj b/Speckle.InterfaceGenerator/Speckle.InterfaceGenerator.csproj
index e6f5c93..af9c35d 100644
--- a/Speckle.InterfaceGenerator/Speckle.InterfaceGenerator.csproj
+++ b/Speckle.InterfaceGenerator/Speckle.InterfaceGenerator.csproj
@@ -11,6 +11,7 @@
         <NoPackageAnalysis>true</NoPackageAnalysis>
         <RootNamespace>Speckle.InterfaceGenerator</RootNamespace>
         <EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>
+        <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     </PropertyGroup>
 
     <PropertyGroup>