diff --git a/src/Functions/DateTimeTransforms.h b/src/Functions/DateTimeTransforms.h
index dfb4b76e5e2..f52c83fa8ab 100644
--- a/src/Functions/DateTimeTransforms.h
+++ b/src/Functions/DateTimeTransforms.h
@@ -63,6 +63,7 @@ constexpr time_t MAX_DATETIME_DAY_NUM =  49710;               // 2106-02-07
 /// This factor transformation will say that the function is monotone everywhere.
 struct ZeroTransform
 {
+    static constexpr auto name = "Zero";
     static UInt16 execute(Int64, const DateLUTImpl &) { return 0; }
     static UInt16 execute(UInt32, const DateLUTImpl &) { return 0; }
     static UInt16 execute(Int32, const DateLUTImpl &) { return 0; }
diff --git a/src/Functions/IFunctionCustomWeek.h b/src/Functions/IFunctionCustomWeek.h
index ba0baa35819..c6f1aebea88 100644
--- a/src/Functions/IFunctionCustomWeek.h
+++ b/src/Functions/IFunctionCustomWeek.h
@@ -55,13 +55,26 @@ public:
                 ? is_monotonic
                 : is_not_monotonic;
         }
-        else
+
+        if (checkAndGetDataType<DataTypeDateTime64>(&type))
         {
-            return Transform::FactorTransform::execute(UInt32(left.safeGet<UInt64>()), date_lut)
-                    == Transform::FactorTransform::execute(UInt32(right.safeGet<UInt64>()), date_lut)
+
+            const auto & left_date_time = left.safeGet<DateTime64>();
+            TransformDateTime64<typename Transform::FactorTransform> transformer_left(left_date_time.getScale());
+
+            const auto & right_date_time = right.safeGet<DateTime64>();
+            TransformDateTime64<typename Transform::FactorTransform> transformer_right(right_date_time.getScale());
+
+            return transformer_left.execute(left_date_time.getValue(), date_lut)
+                    == transformer_right.execute(right_date_time.getValue(), date_lut)
                 ? is_monotonic
                 : is_not_monotonic;
         }
+
+        return Transform::FactorTransform::execute(UInt32(left.safeGet<UInt64>()), date_lut)
+                == Transform::FactorTransform::execute(UInt32(right.safeGet<UInt64>()), date_lut)
+            ? is_monotonic
+            : is_not_monotonic;
     }
 
 protected:
diff --git a/tests/queries/0_stateless/03271_decimal_monotonic_day_of_week.reference b/tests/queries/0_stateless/03271_decimal_monotonic_day_of_week.reference
new file mode 100644
index 00000000000..b8626c4cff2
--- /dev/null
+++ b/tests/queries/0_stateless/03271_decimal_monotonic_day_of_week.reference
@@ -0,0 +1 @@
+4
diff --git a/tests/queries/0_stateless/03271_decimal_monotonic_day_of_week.sql b/tests/queries/0_stateless/03271_decimal_monotonic_day_of_week.sql
new file mode 100644
index 00000000000..66e085c502d
--- /dev/null
+++ b/tests/queries/0_stateless/03271_decimal_monotonic_day_of_week.sql
@@ -0,0 +1,7 @@
+DROP TABLE IF EXISTS decimal_dt;
+
+CREATE TABLE decimal_dt (timestamp DateTime64(9)) ENGINE=MergeTree() ORDER BY timestamp;
+INSERT INTO decimal_dt VALUES (toDate('2024-11-11')),(toDate('2024-11-12')),(toDate('2024-11-13')),(toDate('2024-11-14')),(toDate('2024-11-15')),(toDate('2024-11-16')),(toDate('2024-11-17'));
+SELECT count() FROM decimal_dt WHERE toDayOfWeek(timestamp) > 3;
+
+DROP TABLE IF EXISTS decimal_dt;