diff --git a/src/Npgsql/Internal/TypeInfoMapping.cs b/src/Npgsql/Internal/TypeInfoMapping.cs
index afb5325590..c8439de6ac 100644
--- a/src/Npgsql/Internal/TypeInfoMapping.cs
+++ b/src/Npgsql/Internal/TypeInfoMapping.cs
@@ -71,7 +71,8 @@ public readonly struct TypeInfoMapping(Type type, string dataTypeName, TypeInfoF
     public Func<Type?, bool>? TypeMatchPredicate { get; init; }
 
     public bool TypeEquals(Type type) => TypeMatchPredicate?.Invoke(type) ?? Type == type;
-    public bool DataTypeNameEquals(string dataTypeName)
+
+    private bool DataTypeNameEqualsCore(string dataTypeName)
     {
         var span = DataTypeName.AsSpan();
         return Postgres.DataTypeName.IsFullyQualified(span)
@@ -79,6 +80,18 @@ public bool DataTypeNameEquals(string dataTypeName)
             : span.Equals(Postgres.DataTypeName.ValidatedName(dataTypeName).UnqualifiedNameSpan, StringComparison.Ordinal);
     }
 
+    internal bool DataTypeNameEquals(DataTypeName dataTypeName)
+    {
+        var value = dataTypeName.Value;
+        return DataTypeNameEqualsCore(value);
+    }
+
+    public bool DataTypeNameEquals(string dataTypeName)
+    {
+        var normalized = Postgres.DataTypeName.NormalizeName(dataTypeName);
+        return DataTypeNameEqualsCore(normalized);
+    }
+
     string DebuggerDisplay
     {
         get
@@ -125,7 +138,7 @@ public TypeInfoMappingCollection(IEnumerable<TypeInfoMapping> items)
         {
             var looseTypeMatch = mapping.TypeMatchPredicate is { } pred ? pred(type) : type is null || mapping.Type == type;
             var typeMatch = type is not null && looseTypeMatch;
-            var dataTypeMatch = dataTypeName is not null && mapping.DataTypeNameEquals(dataTypeName.Value.Value);
+            var dataTypeMatch = dataTypeName is not null && mapping.DataTypeNameEquals(dataTypeName.Value);
 
             var matchRequirement = mapping.MatchRequirement;
             if (dataTypeMatch && typeMatch