diff --git a/src/Storages/MergeTree/KeyCondition.cpp b/src/Storages/MergeTree/KeyCondition.cpp
index 79bbc0e7216..970e32f2a70 100644
--- a/src/Storages/MergeTree/KeyCondition.cpp
+++ b/src/Storages/MergeTree/KeyCondition.cpp
@@ -463,7 +463,7 @@ static Field applyFunctionForField(
     return (*block.safeGetByPosition(1).column)[0];
 }
 
-static FieldRef applyFunction(FunctionBasePtr & func, const DataTypePtr & current_type, const FieldRef & field)
+static FieldRef applyFunction(const FunctionBasePtr & func, const DataTypePtr & current_type, const FieldRef & field)
 {
     /// Fallback for fields without block reference.
     if (field.isExplicit())
@@ -1098,10 +1098,10 @@ BoolMask KeyCondition::checkInRange(
 
 std::optional<Range> KeyCondition::applyMonotonicFunctionsChainToRange(
     Range key_range,
-    MonotonicFunctionsChain & functions,
+    const MonotonicFunctionsChain & functions,
     DataTypePtr current_type)
 {
-    for (auto & func : functions)
+    for (const auto & func : functions)
     {
         /// We check the monotonicity of each function on a specific range.
         IFunction::Monotonicity monotonicity = func->getMonotonicityForRange(
diff --git a/src/Storages/MergeTree/KeyCondition.h b/src/Storages/MergeTree/KeyCondition.h
index a37af2d677b..1f2d2f41718 100644
--- a/src/Storages/MergeTree/KeyCondition.h
+++ b/src/Storages/MergeTree/KeyCondition.h
@@ -306,7 +306,7 @@ public:
 
     static std::optional<Range> applyMonotonicFunctionsChainToRange(
         Range key_range,
-        MonotonicFunctionsChain & functions,
+        const MonotonicFunctionsChain & functions,
         DataTypePtr current_type);
 
     bool matchesExactContinuousRange() const;
@@ -349,7 +349,7 @@ private:
         using MergeTreeSetIndexPtr = std::shared_ptr<MergeTreeSetIndex>;
         MergeTreeSetIndexPtr set_index;
 
-        mutable MonotonicFunctionsChain monotonic_functions_chain;    /// The function execution does not violate the constancy.
+        MonotonicFunctionsChain monotonic_functions_chain;
     };
 
     using RPN = std::vector<RPNElement>;