diff --git a/src/Functions/DateTimeTransforms.h b/src/Functions/DateTimeTransforms.h
index 86cedbdec30..6f0bdf406db 100644
--- a/src/Functions/DateTimeTransforms.h
+++ b/src/Functions/DateTimeTransforms.h
@@ -24,7 +24,7 @@ namespace DB
 
 static constexpr auto millisecond_multiplier = 1'000;
 static constexpr auto microsecond_multiplier = 1'000'000;
-static constexpr auto nanosecond_multiplier  = 1'000'000'000;
+static constexpr auto nanosecond_multiplier = 1'000'000'000;
 
 static constexpr FormatSettings::DateTimeOverflowBehavior default_date_time_overflow_behavior = FormatSettings::DateTimeOverflowBehavior::Ignore;
 
@@ -381,11 +381,13 @@ struct ToStartOfWeekImpl
 
     static UInt16 execute(Int64 t, UInt8 week_mode, const DateLUTImpl & time_zone)
     {
-        return time_zone.toFirstDayNumOfWeek(time_zone.toDayNum(t), week_mode);
+        const int res = time_zone.toFirstDayNumOfWeek(time_zone.toDayNum(t), week_mode);
+        return std::max(res, 0);
     }
     static UInt16 execute(UInt32 t, UInt8 week_mode, const DateLUTImpl & time_zone)
     {
-        return time_zone.toFirstDayNumOfWeek(time_zone.toDayNum(t), week_mode);
+        const int res = time_zone.toFirstDayNumOfWeek(time_zone.toDayNum(t), week_mode);
+        return std::max(res, 0);
     }
     static UInt16 execute(Int32 d, UInt8 week_mode, const DateLUTImpl & time_zone)
     {
diff --git a/tests/queries/0_stateless/02403_enable_extended_results_for_datetime_functions.reference b/tests/queries/0_stateless/02403_enable_extended_results_for_datetime_functions.reference
index c830d790000..147e368b5c9 100644
--- a/tests/queries/0_stateless/02403_enable_extended_results_for_datetime_functions.reference
+++ b/tests/queries/0_stateless/02403_enable_extended_results_for_datetime_functions.reference
@@ -64,7 +64,7 @@ toStartOfMonth;toDateTime64;false	2099-07-07
 type;toStartOfMonth;toDateTime64;false	Date
 toStartOfWeek;toDate32;false	2099-07-07
 type;toStartOfWeek;toDate32;false	Date
-toStartOfWeek;toDateTime64;false	2099-07-07
+toStartOfWeek;toDateTime64;false	1970-01-01
 type;toStartOfWeek;toDateTime64;false	Date
 toMonday;toDate32;false	2099-07-08
 type;toMonday;toDate32;false	Date
diff --git a/tests/queries/0_stateless/03215_toStartOfWeek_with_dateTime64_fix.reference b/tests/queries/0_stateless/03215_toStartOfWeek_with_dateTime64_fix.reference
new file mode 100644
index 00000000000..fd698107f22
--- /dev/null
+++ b/tests/queries/0_stateless/03215_toStartOfWeek_with_dateTime64_fix.reference
@@ -0,0 +1,2 @@
+1970-01-01
+1970-01-01
diff --git a/tests/queries/0_stateless/03215_toStartOfWeek_with_dateTime64_fix.sql b/tests/queries/0_stateless/03215_toStartOfWeek_with_dateTime64_fix.sql
new file mode 100644
index 00000000000..1769d96aa8d
--- /dev/null
+++ b/tests/queries/0_stateless/03215_toStartOfWeek_with_dateTime64_fix.sql
@@ -0,0 +1,2 @@
+SELECT toStartOfWeek(toDateTime64('1970-01-01', 6));
+SELECT toStartOfWeek(toDateTime('1970-01-01'));