diff --git a/DuckDB.NET.Bindings/NativeMethods.cs b/DuckDB.NET.Bindings/NativeMethods.cs
index 4f040cc7..ded5c428 100644
--- a/DuckDB.NET.Bindings/NativeMethods.cs
+++ b/DuckDB.NET.Bindings/NativeMethods.cs
@@ -102,7 +102,7 @@ public static class DataChunks
             public static extern IntPtr DuckDBVectorGetData(IntPtr vector);
 
             [DllImport(DuckDbLibrary, CallingConvention = CallingConvention.Cdecl, EntryPoint = "duckdb_vector_get_validity")]
-            public static extern UIntPtr DuckDBVectorGetValidity(IntPtr vector);
+            public static extern IntPtr DuckDBVectorGetValidity(IntPtr vector);
 
             [DllImport(DuckDbLibrary, CallingConvention = CallingConvention.Cdecl, EntryPoint = "duckdb_list_vector_get_child")]
             public static extern long DuckDBListVectorGetChild(IntPtr vector);
@@ -113,7 +113,7 @@ public static class DataChunks
             [DllImport(DuckDbLibrary, CallingConvention = CallingConvention.Cdecl, EntryPoint = "duckdb_struct_vector_get_child")]
             public static extern long DuckDBStructVectorGetChild(IntPtr vector, long index);
         }
-        
+
         public static class Types
         {
             [DllImport(DuckDbLibrary, CallingConvention = CallingConvention.Cdecl, EntryPoint = "duckdb_value_boolean")]
@@ -169,7 +169,7 @@ public static class Types
 
             [DllImport(DuckDbLibrary, CallingConvention = CallingConvention.Cdecl, EntryPoint = "duckdb_value_timestamp")]
             public static extern DuckDBTimestampStruct DuckDBValueTimestamp([In, Out] DuckDBResult result, long col, long row);
-            
+
             [DllImport(DuckDbLibrary, CallingConvention = CallingConvention.Cdecl, EntryPoint = "duckdb_result_get_chunk")]
             public static extern IntPtr DuckDBResultGetChunk(DuckDBResult result, long chunkIndex);
 
@@ -255,7 +255,7 @@ public static class PreparedStatements
             public static extern DuckDBState DuckDBExecutePrepared(DuckDBPreparedStatement preparedStatement, [In, Out] DuckDBResult result);
         }
 
-        public static class ExtractStatements 
+        public static class ExtractStatements
         {
             [DllImport(DuckDbLibrary, CallingConvention = CallingConvention.Cdecl, EntryPoint = "duckdb_extract_statements")]
             public static extern int DuckDBExtractStatements(DuckDBNativeConnection connection, string query, out DuckDBExtractedStatements extractedStatements);
diff --git a/DuckDB.NET.Data/DuckDBDataReader.cs b/DuckDB.NET.Data/DuckDBDataReader.cs
index 931d3150..8c7b4c45 100644
--- a/DuckDB.NET.Data/DuckDBDataReader.cs
+++ b/DuckDB.NET.Data/DuckDBDataReader.cs
@@ -26,7 +26,8 @@ public class DuckDBDataReader : DbDataReader
 
         private int fieldCount;
         private int recordsAffected;
-        private Dictionary<int, IntPtr> vectors = new();
+        private readonly Dictionary<int, IntPtr> vectors = new();
+        private readonly Dictionary<int, IntPtr> vectorValidityMask = new();
 
         internal DuckDBDataReader(DuckDbCommand command, List<DuckDBResult> queryResults, CommandBehavior behavior)
         {
@@ -50,6 +51,7 @@ private void InitReaderData()
             for (int i = 0; i < columnCount; i++)
             {
                 vectors[i] = NativeMethods.DataChunks.DuckDBDataChunkGetVector(chunk, i);
+                vectorValidityMask[i] = (NativeMethods.DataChunks.DuckDBVectorGetValidity(vectors[i]));
             }
 
             currentRow = -1;
@@ -120,6 +122,7 @@ private DuckDBTimeOnly GetTimeOnly(int ordinal)
 
         public override decimal GetDecimal(int ordinal)
         {
+            return 0;
             return decimal.Parse(GetString(ordinal), CultureInfo.InvariantCulture);
         }
 
@@ -153,8 +156,7 @@ public override Type GetFieldType(int ordinal)
                 DuckDBType.DuckdbTypeVarchar => typeof(string),
                 DuckDBType.DuckdbTypeDecimal => typeof(decimal),
                 DuckDBType.DuckdbTypeBlob => typeof(Stream),
-                var type => throw new ArgumentException(
-                    $"Unrecognised type {type} ({(int)type}) in column {ordinal + 1}")
+                var type => throw new ArgumentException($"Unrecognised type {type} ({(int)type}) in column {ordinal + 1}")
             };
         }
 
@@ -235,6 +237,11 @@ public override int GetOrdinal(string name)
 
         public override string GetString(int ordinal)
         {
+            if (IsDBNull(ordinal))
+            {
+                return null;
+            }
+
             var data = NativeMethods.DataChunks.DuckDBVectorGetData(vectors[ordinal]);
             data += currentRow * Marshal.SizeOf<DuckDBString>();
 
@@ -309,9 +316,14 @@ public override Stream GetStream(int ordinal)
 
         public override bool IsDBNull(int ordinal)
         {
-            return false;
-            var nullMask = NativeMethods.Query.DuckDBNullmaskData(currentResult, ordinal);
-            return Marshal.ReadByte(nullMask, currentRow) != 0;
+            var validityMaskEntryIndex = currentRow / 64;
+            var validityBitIndex = currentRow % 64;
+
+            var validityMaskEntryPtr = vectorValidityMask[ordinal] + validityMaskEntryIndex;
+            var validityBit = 1ul << validityBitIndex;
+
+            var isValid = (Marshal.PtrToStructure<ulong>(validityMaskEntryPtr) & validityBit) != 0;
+            return !isValid;
         }
 
         public override int FieldCount => fieldCount;
@@ -329,11 +341,11 @@ public override bool IsDBNull(int ordinal)
         public override bool NextResult()
         {
             currentResultIndex++;
-            
+
             if (currentResultIndex < queryResults.Count)
             {
                 currentResult = queryResults[currentResultIndex];
-                
+
                 InitReaderData();
                 return true;
             }