diff --git a/src/Functions/toStartOfInterval.cpp b/src/Functions/toStartOfInterval.cpp
index e358addf972..cc5ffd56976 100644
--- a/src/Functions/toStartOfInterval.cpp
+++ b/src/Functions/toStartOfInterval.cpp
@@ -192,6 +192,8 @@ public:
             case ResultType::DateTime64:
             {
                 UInt32 scale = 0;
+                if (isDateTime64(arguments[0].type) && overload == Overload::Origin)
+                    scale = assert_cast<const DataTypeDateTime64 &>(*arguments[0].type.get()).getScale();
                 if (interval_type->getKind() == IntervalKind::Kind::Nanosecond)
                     scale = (9 > scale) ? 9 : scale;
                 else if (interval_type->getKind() == IntervalKind::Kind::Microsecond)