diff --git a/src/Umbraco.Core/Collections/CompositeNStringNStringKey.cs b/src/Umbraco.Core/Collections/CompositeNStringNStringKey.cs
new file mode 100644
index 0000000000..a06696f6c6
--- /dev/null
+++ b/src/Umbraco.Core/Collections/CompositeNStringNStringKey.cs
@@ -0,0 +1,41 @@
+using System;
+
+namespace Umbraco.Core.Collections
+{
+    /// <summary>
+    /// Represents a composite key of (string, string) for fast dictionaries.
+    /// </summary>
+    /// <remarks>
+    /// <para>The string parts of the key are case-insensitive.</para>
+    /// <para>Null is a valid value for both parts.</para>
+    /// </remarks>
+    public struct CompositeNStringNStringKey : IEquatable<CompositeNStringNStringKey>
+    {
+        private readonly string _key1;
+        private readonly string _key2;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="CompositeNStringNStringKey"/> struct.
+        /// </summary>
+        public CompositeNStringNStringKey(string key1, string key2)
+        {
+            _key1 = key1?.ToLowerInvariant() ?? "NULL";
+            _key2 = key2?.ToLowerInvariant() ?? "NULL";
+        }
+
+        public bool Equals(CompositeNStringNStringKey other)
+            => _key2 == other._key2 && _key1 == other._key1;
+
+        public override bool Equals(object obj)
+            => obj is CompositeNStringNStringKey other && _key2 == other._key2 && _key1 == other._key1;
+
+        public override int GetHashCode()
+            => _key2.GetHashCode() * 31 + _key1.GetHashCode();
+
+        public static bool operator ==(CompositeNStringNStringKey key1, CompositeNStringNStringKey key2)
+            => key1._key2 == key2._key2 && key1._key1 == key2._key1;
+
+        public static bool operator !=(CompositeNStringNStringKey key1, CompositeNStringNStringKey key2)
+            => key1._key2 != key2._key2 || key1._key1 != key2._key1;
+    }
+}
\ No newline at end of file
diff --git a/src/Umbraco.Core/Collections/CompositeStringStringKey.cs b/src/Umbraco.Core/Collections/CompositeStringStringKey.cs
index 78ee9b0d2a..c053b08a22 100644
--- a/src/Umbraco.Core/Collections/CompositeStringStringKey.cs
+++ b/src/Umbraco.Core/Collections/CompositeStringStringKey.cs
@@ -7,7 +7,7 @@ namespace Umbraco.Core.Collections
     /// </summary>
     /// <remarks>
     /// <para>The string parts of the key are case-insensitive.</para>
-    /// <para>Null is a valid value for both parts.</para>
+    /// <para>Null is NOT a valid value for neither parts.</para>
     /// </remarks>
     public struct CompositeStringStringKey : IEquatable<CompositeStringStringKey>
     {
@@ -19,12 +19,8 @@ namespace Umbraco.Core.Collections
         /// </summary>
         public CompositeStringStringKey(string key1, string key2)
         {
-            // fixme temp - debugging
-            if (key1 == null) throw new Exception("Getting null culture in CompositeStringStringKey constructor, fix!");
-            if (key2 == null) throw new Exception("Getting null segment in CompositeStringStringKey constructor, fix!");
-
-            _key1 = key1?.ToLowerInvariant() ?? "NULL";
-            _key2 = key2?.ToLowerInvariant() ?? "NULL";
+            _key1 = key1?.ToLowerInvariant() ?? throw new ArgumentNullException(nameof(key1));
+            _key2 = key2?.ToLowerInvariant() ?? throw new ArgumentNullException(nameof(key2));
         }
 
         public bool Equals(CompositeStringStringKey other)
diff --git a/src/Umbraco.Core/Models/Property.cs b/src/Umbraco.Core/Models/Property.cs
index 7e53eb764a..19a63925df 100644
--- a/src/Umbraco.Core/Models/Property.cs
+++ b/src/Umbraco.Core/Models/Property.cs
@@ -18,7 +18,7 @@ namespace Umbraco.Core.Models
     {
         private List<PropertyValue> _values = new List<PropertyValue>();
         private PropertyValue _pvalue;
-        private Dictionary<CompositeStringStringKey, PropertyValue> _vvalues;
+        private Dictionary<CompositeNStringNStringKey, PropertyValue> _vvalues;
 
         private static readonly Lazy<PropertySelectors> Ps = new Lazy<PropertySelectors>();
 
@@ -77,8 +77,8 @@ namespace Umbraco.Core.Models
 
                     // custom comparer for enumerable
                     // ReSharper disable once MergeCastWithTypeCheck
-                    if (o is IEnumerable && o1 is IEnumerable)
-                        return ((IEnumerable) o).Cast<object>().UnsortedSequenceEqual(((IEnumerable) o1).Cast<object>());
+                    if (o is IEnumerable && o1 is IEnumerable enumerable)
+                        return ((IEnumerable) o).Cast<object>().UnsortedSequenceEqual(enumerable.Cast<object>());
 
                     return o.Equals(o1);
                 }, o => o.GetHashCode());
@@ -104,7 +104,7 @@ namespace Umbraco.Core.Models
                 _values = value.Where(x => PropertyType.ValidateVariation(x.Culture, x.Segment, false)).ToList();
                 _pvalue = _values.FirstOrDefault(x => x.Culture == null && x.Segment == null);
                 _vvalues = _values.Count > (_pvalue == null ? 0 : 1)
-                    ? _values.Where(x => x != _pvalue).ToDictionary(x => new CompositeStringStringKey(x.Culture, x.Segment), x => x)
+                    ? _values.Where(x => x != _pvalue).ToDictionary(x => new CompositeNStringNStringKey(x.Culture, x.Segment), x => x)
                     : null;
             }
         }
@@ -138,7 +138,7 @@ namespace Umbraco.Core.Models
             if (!PropertyType.ValidateVariation(culture, segment, false)) return null;
             if (culture == null && segment == null) return GetPropertyValue(_pvalue, published);
             if (_vvalues == null) return null;
-            return _vvalues.TryGetValue(new CompositeStringStringKey(culture, segment), out var pvalue)
+            return _vvalues.TryGetValue(new CompositeNStringNStringKey(culture, segment), out var pvalue)
                 ? GetPropertyValue(pvalue, published)
                 : null;
         }
@@ -177,7 +177,7 @@ namespace Umbraco.Core.Models
         {
             PropertyType.ValidateVariation(culture, segment, true);
 
-            (var pvalue, _) = GetPValue(culture, segment, false);
+            var (pvalue, _) = GetPValue(culture, segment, false);
             if (pvalue == null) return;
             PublishPropertyValue(pvalue);
         }
@@ -222,7 +222,7 @@ namespace Umbraco.Core.Models
         internal void ClearPublishedValue(string culture = null, string segment = null)
         {
             PropertyType.ValidateVariation(culture, segment, true);
-            (var pvalue, _) = GetPValue(culture, segment, false);
+            var (pvalue, _) = GetPValue(culture, segment, false);
             if (pvalue == null) return;
             ClearPublishedPropertyValue(pvalue);
         }
@@ -271,12 +271,8 @@ namespace Umbraco.Core.Models
         /// </summary>
         public void SetValue(object value, string culture = null, string segment = null)
         {
-            if (PropertyType.Variations == ContentVariation.InvariantNeutral)
-            {
-                culture = null;
-            }
             PropertyType.ValidateVariation(culture, segment, true);
-            (var pvalue, var change) = GetPValue(culture, segment, true);
+            var (pvalue, change) = GetPValue(culture, segment, true);
 
             var origValue = pvalue.EditedValue;
             var setValue = PropertyType.ConvertAssignedValue(value);
@@ -289,7 +285,7 @@ namespace Umbraco.Core.Models
         // bypasses all changes detection and is the *only* way to set the published value
         internal void FactorySetValue(string culture, string segment, bool published, object value)
         {
-            (var pvalue, _) = GetPValue(culture, segment, true);
+            var (pvalue, _) = GetPValue(culture, segment, true);
 
             if (published && PropertyType.IsPublishing)
                 pvalue.PublishedValue = value;
@@ -319,10 +315,10 @@ namespace Umbraco.Core.Models
             if (_vvalues == null)
             {
                 if (!create) return (null, false);
-                _vvalues = new Dictionary<CompositeStringStringKey, PropertyValue>();
+                _vvalues = new Dictionary<CompositeNStringNStringKey, PropertyValue>();
                 change = true;
             }
-            var k = new CompositeStringStringKey(culture, segment);
+            var k = new CompositeNStringNStringKey(culture, segment);
             if (!_vvalues.TryGetValue(k, out var pvalue))
             {
                 if (!create) return (null, false);
diff --git a/src/Umbraco.Core/Umbraco.Core.csproj b/src/Umbraco.Core/Umbraco.Core.csproj
index 384f1defa6..10d9277ccf 100644
--- a/src/Umbraco.Core/Umbraco.Core.csproj
+++ b/src/Umbraco.Core/Umbraco.Core.csproj
@@ -136,6 +136,7 @@
     <Compile Include="CodeAnnotations\UmbracoProposedPublicAttribute.cs" />
     <Compile Include="CodeAnnotations\UmbracoUdiTypeAttribute.cs" />
     <Compile Include="CodeAnnotations\UmbracoWillObsoleteAttribute.cs" />
+    <Compile Include="Collections\CompositeNStringNStringKey.cs" />
     <Compile Include="Collections\CompositeStringStringKey.cs" />
     <Compile Include="Collections\CompositeIntStringKey.cs" />
     <Compile Include="Collections\CompositeTypeTypeKey.cs" />
diff --git a/src/Umbraco.Tests/Services/EntityServiceTests.cs b/src/Umbraco.Tests/Services/EntityServiceTests.cs
index 5cb59fecbe..205507cce8 100644
--- a/src/Umbraco.Tests/Services/EntityServiceTests.cs
+++ b/src/Umbraco.Tests/Services/EntityServiceTests.cs
@@ -499,9 +499,10 @@ namespace Umbraco.Tests.Services
 
             for (int i = 0; i < entities.Length; i++)
             {
+                Assert.AreEqual(0, entities[i].AdditionalData.Count);
+
                 if (i % 2 == 0)
                 {
-                    Assert.AreEqual(1, entities[i].AdditionalData.Count);
                     var doc = (IDocumentEntitySlim)entities[i];
                     var keys = doc.CultureNames.Keys.ToList();
                     var vals = doc.CultureNames.Values.ToList();
diff --git a/src/Umbraco.Web/Models/Mapping/ContentPropertyBasicConverter.cs b/src/Umbraco.Web/Models/Mapping/ContentPropertyBasicConverter.cs
index aec5c375d9..b5070ae8ad 100644
--- a/src/Umbraco.Web/Models/Mapping/ContentPropertyBasicConverter.cs
+++ b/src/Umbraco.Web/Models/Mapping/ContentPropertyBasicConverter.cs
@@ -53,11 +53,6 @@ namespace Umbraco.Web.Models.Mapping
                 //a language Id needs to be set for a property type that can be varried by language
                 throw new InvalidOperationException($"No languageId found in mapping operation when one is required for the culture neutral property type {property.PropertyType.Alias}");
             }
-            if (property.PropertyType.Variations == ContentVariation.InvariantNeutral)
-            {
-                culture = null;
-
-            }
 
             var result = new TDestination
                 {