diff --git a/src/Functions/GatherUtils/Sources.h b/src/Functions/GatherUtils/Sources.h
index cc7f2b662b6..2795b7ac4ed 100644
--- a/src/Functions/GatherUtils/Sources.h
+++ b/src/Functions/GatherUtils/Sources.h
@@ -573,7 +573,7 @@ struct GenericArraySource : public ArraySourceImpl<GenericArraySource>
 
     size_t getSizeForReserve() const override
     {
-        return elements.size();
+        return offsets.size();
     }
 
     size_t getColumnSize() const override