diff --git a/TunnelVisionLabs.ReferenceAssemblyAnnotator/AnnotatorBuildTask.cs b/TunnelVisionLabs.ReferenceAssemblyAnnotator/AnnotatorBuildTask.cs
index f992064..1e157f0 100644
--- a/TunnelVisionLabs.ReferenceAssemblyAnnotator/AnnotatorBuildTask.cs
+++ b/TunnelVisionLabs.ReferenceAssemblyAnnotator/AnnotatorBuildTask.cs
@@ -74,7 +74,7 @@ public override bool Execute()
         {
             var log = new SuppressibleLoggingHelper(Log, requiredPrefix: "RA", DisabledWarnings);
 
-            string unannotatedReferenceAssembly = TargetFrameworkDirectories.Select(path => Path.Combine(path.ItemSpec, UnannotatedReferenceAssembly + ".dll")).FirstOrDefault(File.Exists);
+            string? unannotatedReferenceAssembly = TargetFrameworkDirectories.Select(path => Path.Combine(path.ItemSpec, UnannotatedReferenceAssembly + ".dll")).FirstOrDefault(File.Exists);
             string annotatedReferenceAssembly = Path.Combine(AnnotatedReferenceAssemblyDirectory, UnannotatedReferenceAssembly + ".dll");
             bool foundAnnotatedAssembly = File.Exists(annotatedReferenceAssembly);
 
diff --git a/TunnelVisionLabs.ReferenceAssemblyAnnotator/Program.cs b/TunnelVisionLabs.ReferenceAssemblyAnnotator/Program.cs
index a79fc55..878d0c4 100644
--- a/TunnelVisionLabs.ReferenceAssemblyAnnotator/Program.cs
+++ b/TunnelVisionLabs.ReferenceAssemblyAnnotator/Program.cs
@@ -287,7 +287,7 @@ private static bool IsExcludedAnnotation(ICustomAttributeProvider provider, ICus
             return annotatedTypeDefinition;
         }
 
-        private static MethodDefinition FindMatchingMethod(SuppressibleLoggingHelper? log, MethodDefinition methodDefinition, TypeDefinition annotatedTypeDefinition)
+        private static MethodDefinition? FindMatchingMethod(SuppressibleLoggingHelper? log, MethodDefinition methodDefinition, TypeDefinition annotatedTypeDefinition)
         {
             try
             {
@@ -305,12 +305,12 @@ private static MethodDefinition FindMatchingMethod(SuppressibleLoggingHelper? lo
             }
         }
 
-        private static PropertyDefinition FindMatchingProperty(PropertyDefinition propertyDefinition, TypeDefinition annotatedTypeDefinition)
+        private static PropertyDefinition? FindMatchingProperty(PropertyDefinition propertyDefinition, TypeDefinition annotatedTypeDefinition)
         {
             return annotatedTypeDefinition.Properties.SingleOrDefault(property => EquivalenceComparers.PropertyDefinition.Equals(propertyDefinition, property));
         }
 
-        private static FieldDefinition FindMatchingField(FieldDefinition fieldDefinition, TypeDefinition annotatedTypeDefinition)
+        private static FieldDefinition? FindMatchingField(FieldDefinition fieldDefinition, TypeDefinition annotatedTypeDefinition)
         {
             return annotatedTypeDefinition.Fields.SingleOrDefault(property => property.Name == fieldDefinition.Name);
         }