diff --git a/src/JsonApiDotNetCore/Queries/Parsing/ConstantValueConverter.cs b/src/JsonApiDotNetCore/Queries/Parsing/ConstantValueConverter.cs
new file mode 100644
index 0000000000..d624964ddd
--- /dev/null
+++ b/src/JsonApiDotNetCore/Queries/Parsing/ConstantValueConverter.cs
@@ -0,0 +1,15 @@
+namespace JsonApiDotNetCore.Queries.Parsing;
+
+/// <summary>
+/// Converts a constant value within a query string parameter to an <see cref="object" />.
+/// </summary>
+/// <param name="value">
+/// The constant value to convert from.
+/// </param>
+/// <param name="position">
+/// The zero-based position of <paramref name="value" /> in the query string parameter value.
+/// </param>
+/// <returns>
+/// The converted object instance.
+/// </returns>
+public delegate object ConstantValueConverter(string value, int position);
diff --git a/src/JsonApiDotNetCore/Queries/Parsing/FilterParser.cs b/src/JsonApiDotNetCore/Queries/Parsing/FilterParser.cs
index cbd6ee4b21..19757bbd08 100644
--- a/src/JsonApiDotNetCore/Queries/Parsing/FilterParser.cs
+++ b/src/JsonApiDotNetCore/Queries/Parsing/FilterParser.cs
@@ -252,13 +252,13 @@ private QueryExpression ParseComparisonRightTerm(QueryExpression leftTerm)
 
             var leftAttribute = (AttrAttribute)leftLastField;
 
-            Func<string, int, object> constantValueConverter = GetConstantValueConverterForAttribute(leftAttribute);
+            ConstantValueConverter constantValueConverter = GetConstantValueConverterForAttribute(leftAttribute);
             return ParseTypedComparisonRightTerm(leftAttribute.Property.PropertyType, constantValueConverter);
         }
 
         if (leftTerm is FunctionExpression leftFunction)
         {
-            Func<string, int, object> constantValueConverter = GetConstantValueConverterForType(leftFunction.ReturnType);
+            ConstantValueConverter constantValueConverter = GetConstantValueConverterForType(leftFunction.ReturnType);
             return ParseTypedComparisonRightTerm(leftFunction.ReturnType, constantValueConverter);
         }
 
@@ -266,7 +266,7 @@ private QueryExpression ParseComparisonRightTerm(QueryExpression leftTerm)
             $"Internal error: Expected left term to be a function or field chain, instead of '{leftTerm.GetType().Name}': '{leftTerm}'.");
     }
 
-    private QueryExpression ParseTypedComparisonRightTerm(Type leftType, Func<string, int, object> constantValueConverter)
+    private QueryExpression ParseTypedComparisonRightTerm(Type leftType, ConstantValueConverter constantValueConverter)
     {
         bool allowNull = RuntimeTypeConverter.CanContainNull(leftType);
 
@@ -329,7 +329,7 @@ protected virtual MatchTextExpression ParseTextMatch(string operatorName)
 
         EatSingleCharacterToken(TokenKind.Comma);
 
-        Func<string, int, object> constantValueConverter = GetConstantValueConverterForAttribute(targetAttribute);
+        ConstantValueConverter constantValueConverter = GetConstantValueConverterForAttribute(targetAttribute);
         LiteralConstantExpression constant = ParseConstant(constantValueConverter);
 
         EatSingleCharacterToken(TokenKind.CloseParen);
@@ -352,7 +352,7 @@ protected virtual AnyExpression ParseAny()
 
         ImmutableHashSet<LiteralConstantExpression>.Builder constantsBuilder = ImmutableHashSet.CreateBuilder<LiteralConstantExpression>();
 
-        Func<string, int, object> constantValueConverter = GetConstantValueConverterForAttribute(targetAttribute);
+        ConstantValueConverter constantValueConverter = GetConstantValueConverterForAttribute(targetAttribute);
         LiteralConstantExpression constant = ParseConstant(constantValueConverter);
         constantsBuilder.Add(constant);
 
@@ -489,7 +489,7 @@ private static ResourceType ResolveDerivedType(ResourceType baseType, string der
         return filter;
     }
 
-    private LiteralConstantExpression ParseConstant(Func<string, int, object> constantValueConverter)
+    private LiteralConstantExpression ParseConstant(ConstantValueConverter constantValueConverter)
     {
         int position = GetNextTokenPositionOrEnd();
 
@@ -514,7 +514,7 @@ private NullConstantExpression ParseNull()
         throw new QueryParseException("null expected.", position);
     }
 
-    private static Func<string, int, object> GetConstantValueConverterForType(Type destinationType)
+    protected virtual ConstantValueConverter GetConstantValueConverterForType(Type destinationType)
     {
         return (stringValue, position) =>
         {
@@ -529,7 +529,7 @@ private static Func<string, int, object> GetConstantValueConverterForType(Type d
         };
     }
 
-    private Func<string, int, object> GetConstantValueConverterForAttribute(AttrAttribute attribute)
+    private ConstantValueConverter GetConstantValueConverterForAttribute(AttrAttribute attribute)
     {
         if (attribute is { Property.Name: nameof(Identifiable<object>.Id) })
         {