diff --git a/S7.Net.UnitTest/S7NetTestsSync.cs b/S7.Net.UnitTest/S7NetTestsSync.cs
index 85e22461..7128a6ce 100644
--- a/S7.Net.UnitTest/S7NetTestsSync.cs
+++ b/S7.Net.UnitTest/S7NetTestsSync.cs
@@ -1015,6 +1015,17 @@ public void T26_ReadWriteDouble()
             Assert.AreEqual(test_value, result, "Compare Write/Read");
         }
 
+        [TestMethod]
+        public void T26_ReadWriteDoubles()
+        {
+          double[] test_values = [ 55.66, 89.88 ];
+          plc.Write(DataType.DataBlock, 1, 0, test_values);
+          var result = (double[])plc.Read(DataType.DataBlock, 1, 0, VarType.LReal, 2);
+
+          Assert.AreEqual(test_values[0], result[0], "Compare Write/Read 0");
+          Assert.AreEqual(test_values[1], result[1], "Compare Write/Read 1");
+        }
+
         [TestMethod]
         public void T27_ReadWriteBytesMany()
         {
diff --git a/S7.Net/Types/TypeHelper.cs b/S7.Net/Types/TypeHelper.cs
index af5441b1..68c93bf2 100644
--- a/S7.Net/Types/TypeHelper.cs
+++ b/S7.Net/Types/TypeHelper.cs
@@ -11,11 +11,12 @@ internal static class TypeHelper
         /// </summary>
         public static byte[] ToByteArray<T>(T[] value, Func<T, byte[]> converter) where T : struct
         {
-            var buffer = new byte[Marshal.SizeOf(default(T)) * value.Length];
+            var typeSize = Marshal.SizeOf(default(T));
+            var buffer = new byte[typeSize * value.Length];
             var stream = new MemoryStream(buffer);
             foreach (var val in value)
             {
-                stream.Write(converter(val), 0, 4);
+                stream.Write(converter(val), 0, typeSize);
             }
 
             return buffer;