diff --git a/ClickHouse.Client.Tests/TestUtilities.cs b/ClickHouse.Client.Tests/TestUtilities.cs
index 05b6b573..b6b2022e 100644
--- a/ClickHouse.Client.Tests/TestUtilities.cs
+++ b/ClickHouse.Client.Tests/TestUtilities.cs
@@ -80,6 +80,10 @@ public static IEnumerable<DataTypeSample> GetDataTypeSamples()
             yield return new DataTypeSample("Decimal64(7)", typeof(decimal), "toDecimal64(1.2345, 7)", new decimal(1.2345));
             yield return new DataTypeSample("Decimal128(9)", typeof(decimal), "toDecimal128(12.34, 9)", new decimal(12.34));
 
+            yield return new DataTypeSample("Decimal32(3)", typeof(decimal), "toDecimal32(-123.45, 3)", new decimal(-123.45));
+            yield return new DataTypeSample("Decimal64(7)", typeof(decimal), "toDecimal64(-1.2345, 7)", new decimal(-1.2345));
+            yield return new DataTypeSample("Decimal128(9)", typeof(decimal), "toDecimal128(-12.34, 9)", new decimal(-12.34));
+
             yield return new DataTypeSample("Array(Int32)", typeof(int[]), "array(1, 2, 3)", new[] { 1, 2, 3 });
 
             yield return new DataTypeSample("Nullable(Int32)", typeof(int?), "toInt32OrNull('123')", 123);
diff --git a/ClickHouse.Client/Formats/BinaryStreamWriter.cs b/ClickHouse.Client/Formats/BinaryStreamWriter.cs
index 59d6bddc..5c248421 100644
--- a/ClickHouse.Client/Formats/BinaryStreamWriter.cs
+++ b/ClickHouse.Client/Formats/BinaryStreamWriter.cs
@@ -61,9 +61,18 @@ public void WriteValue(object data, ClickHouseType databaseType)
                 case ClickHouseTypeCode.Decimal:
                     var dti = (DecimalType)databaseType;
                     var value = new BigInteger(MathUtils.ShiftDecimalPlaces(Convert.ToDecimal(data), dti.Scale));
-                    var dbytes = new byte[dti.Size];
-                    value.ToByteArray().CopyTo(dbytes, 0);
-                    writer.Write(dbytes);
+                    var biBytes = value.ToByteArray();
+                    var decimalBytes = new byte[dti.Size];
+                    biBytes.CopyTo(decimalBytes, 0);
+
+                    // If a negative BigInteger is not long enough to fill the whole buffer, the remainder needs to be filled with 0xFF
+                    if (value < 0)
+                    {
+                        for (int i = biBytes.Length; i < dti.Size; i++)
+                            decimalBytes[i] = 0xFF;
+                    }
+
+                    writer.Write(decimalBytes);
                     break;
 
                 case ClickHouseTypeCode.String: