diff --git a/src/Storages/MergeTree/MergeTask.cpp b/src/Storages/MergeTree/MergeTask.cpp
index 75fd61ae4be..cafc11fc34d 100644
--- a/src/Storages/MergeTree/MergeTask.cpp
+++ b/src/Storages/MergeTree/MergeTask.cpp
@@ -195,7 +195,7 @@ void MergeTask::ExecuteAndFinalizeHorizontalPart::extractMergingAndGatheringColu
     }
 }
 
-bool MergeTask::ExecuteAndFinalizeHorizontalPart::prepare()
+bool MergeTask::ExecuteAndFinalizeHorizontalPart::prepare() const
 {
     ProfileEvents::increment(ProfileEvents::Merge);
 
@@ -657,7 +657,7 @@ void MergeTask::ExecuteAndFinalizeHorizontalPart::constructTaskForProjectionPart
 }
 
 
-bool MergeTask::ExecuteAndFinalizeHorizontalPart::executeMergeProjections() // NOLINT
+bool MergeTask::ExecuteAndFinalizeHorizontalPart::executeMergeProjections() const
 {
     /// In case if there are no projections we didn't construct a task
     if (!ctx->merge_projection_parts_task_ptr)
@@ -676,7 +676,7 @@ bool MergeTask::ExecuteAndFinalizeHorizontalPart::executeMergeProjections() // N
     return true;
 }
 
-bool MergeTask::ExecuteAndFinalizeHorizontalPart::executeImpl()
+bool MergeTask::ExecuteAndFinalizeHorizontalPart::executeImpl() const
 {
     Stopwatch watch(CLOCK_MONOTONIC_COARSE);
     UInt64 step_time_ms = global_ctx->data->getSettings()->background_task_preferred_step_execution_time_ms.totalMilliseconds();
diff --git a/src/Storages/MergeTree/MergeTask.h b/src/Storages/MergeTree/MergeTask.h
index b36f5f832d9..a30ab4712d5 100644
--- a/src/Storages/MergeTree/MergeTask.h
+++ b/src/Storages/MergeTree/MergeTask.h
@@ -268,12 +268,12 @@ private:
     {
         bool execute() override;
 
-        bool prepare();
-        bool executeImpl();
+        bool prepare() const;
+        bool executeImpl() const;
         void finalize() const;
 
         /// NOTE: Using pointer-to-member instead of std::function and lambda makes stacktraces much more concise and readable
-        using ExecuteAndFinalizeHorizontalPartSubtasks = std::array<bool(ExecuteAndFinalizeHorizontalPart::*)(), 3>;
+        using ExecuteAndFinalizeHorizontalPartSubtasks = std::array<bool(ExecuteAndFinalizeHorizontalPart::*)()const, 3>;
 
         const ExecuteAndFinalizeHorizontalPartSubtasks subtasks
         {
@@ -288,7 +288,7 @@ private:
         void calculateProjections(const Block & block) const;
         void finalizeProjections() const;
         void constructTaskForProjectionPartsMerge() const;
-        bool executeMergeProjections();
+        bool executeMergeProjections() const;
 
         MergeAlgorithm chooseMergeAlgorithm() const;
         void createMergedStream() const;