diff --git a/src/Core/Settings.h b/src/Core/Settings.h
index 1d1a255054a..593bcab43d6 100644
--- a/src/Core/Settings.h
+++ b/src/Core/Settings.h
@@ -484,8 +484,8 @@ class IColumn;
     M(Bool, allow_non_metadata_alters, true, "Allow to execute alters which affects not only tables metadata, but also data on disk", 0) \
     M(Bool, enable_global_with_statement, true, "Propagate WITH statements to UNION queries and all subqueries", 0) \
     M(Bool, aggregate_functions_null_for_empty, false, "Rewrite all aggregate functions in a query, adding -OrNull suffix to them", 0) \
-    M(Bool, optimize_syntax_fuse_functions, true, "Allow apply syntax optimisation: fuse aggregate functions", 0) \
-    M(Bool, optimize_fuse_sum_count_avg, true, "Fuse functions `sum, avg, count` with identical arguments into one `sumCount` (`optimize_syntax_fuse_functions should be enabled)", 0) \
+    M(Bool, optimize_syntax_fuse_functions, false, "Not ready for production, do not use. Allow apply syntax optimisation: fuse aggregate functions", 0) \
+    M(Bool, optimize_fuse_sum_count_avg, false, "Not ready for production, do not use. Fuse functions `sum, avg, count` with identical arguments into one `sumCount` (`optimize_syntax_fuse_functions should be enabled)", 0) \
     M(Bool, flatten_nested, true, "If true, columns of type Nested will be flatten to separate array columns instead of one array of tuples", 0) \
     M(Bool, asterisk_include_materialized_columns, false, "Include MATERIALIZED columns for wildcard query", 0) \
     M(Bool, asterisk_include_alias_columns, false, "Include ALIAS columns for wildcard query", 0) \