diff --git a/src/AggregateFunctions/AggregateFunctionAvg.h b/src/AggregateFunctions/AggregateFunctionAvg.h
index 5dd6cf856ef..a35e1a965a9 100644
--- a/src/AggregateFunctions/AggregateFunctionAvg.h
+++ b/src/AggregateFunctions/AggregateFunctionAvg.h
@@ -17,8 +17,10 @@ using DecimalOrVectorCol = std::conditional_t<IsDecimalNumber<T>, ColumnDecimal<
 template <class Numerator, class Denominator>
 struct RationalFraction
 {
-    Numerator numerator{0};
-    Denominator denominator{0};
+    /// {0} prohibited as excess elements.
+    /// = 0 prohibited as there are no suitable constructors.
+    Numerator numerator = static_cast<Numerator>(0);
+    Denominator denominator = static_cast<Denominator>(0);
 
     /// Calculate the fraction as a #Result.
     template <class Result>