diff --git a/src/Storages/MergeTree/MutateTask.cpp b/src/Storages/MergeTree/MutateTask.cpp
index 712835ede1c..5e30cafdee4 100644
--- a/src/Storages/MergeTree/MutateTask.cpp
+++ b/src/Storages/MergeTree/MutateTask.cpp
@@ -1015,6 +1015,7 @@ struct MutationContext
 
     FutureMergedMutatedPartPtr future_part;
     MergeTreeData::DataPartPtr source_part;
+    MergeTreeData::DataPartPtr projection_part;
     StorageMetadataPtr metadata_snapshot;
 
     MutationCommandsConstPtr commands;
@@ -1027,13 +1028,16 @@ struct MutationContext
     std::unique_ptr<CurrentMetrics::Increment> num_mutations;
 
     QueryPipelineBuilder mutating_pipeline_builder;
-    /// source here is projection part instead of table part
-    QueryPipelineBuilder projection_mutating_pipeline_builder;
     QueryPipeline mutating_pipeline; // in
     std::unique_ptr<PullingPipelineExecutor> mutating_executor;
     ProgressCallback progress_callback;
     Block updated_header;
 
+    /// source here is projection part instead of table part
+    QueryPipelineBuilder projection_mutating_pipeline_builder;
+    QueryPipeline projection_mutating_pipeline;
+    std::unique_ptr<PullingPipelineExecutor> projection_mutating_executor;
+
     std::unique_ptr<MutationsInterpreter> interpreter;
     UInt64 watch_prev_elapsed = 0;
     std::unique_ptr<MergeStageProgress> stage_progress;
@@ -1050,6 +1054,9 @@ struct MutationContext
     MergeTreeData::MutableDataPartPtr new_data_part;
     IMergedBlockOutputStreamPtr out;
 
+    MergeTreeData::MutableDataPartPtr new_projection_part;
+    IMergedBlockOutputStreamPtr projection_out;
+
     String mrk_extension;
 
     /// Used in lightweight delete to bit mask the projection if possible,
@@ -1886,6 +1893,26 @@ private:
 
             ctx->projections_to_build = std::vector<ProjectionDescriptionRawPtr>{ctx->projections_to_recalc.begin(), ctx->projections_to_recalc.end()};
 
+            chassert (ctx->projection_mutating_pipeline_builder.initialized());
+            builder = std::make_unique<QueryPipelineBuilder>(std::move(ctx->projection_mutating_pipeline_builder));
+
+            // ctx->projection_out = std::make_shared<MergedColumnOnlyOutputStream>(
+            //     ctx->new_projection_part,
+            //     ctx->metadata_snapshot,
+            //     ctx->updated_header.getNamesAndTypesList(),
+            //     ctx->compression_codec,
+            //     std::vector<MergeTreeIndexPtr>(),
+            //     std::vector<ColumnStatisticsPartPtr>(),
+            //     nullptr,
+            //     /*save_marks_in_cache=*/ false,
+            //     ctx->projection_part->index_granularity,
+            //     &ctx->projection_part->index_granularity_info
+            // );
+
+            ctx->projection_mutating_pipeline = QueryPipelineBuilder::getPipeline(std::move(*builder));
+            ctx->projection_mutating_pipeline.disableProfileEventUpdate();
+            ctx->projection_mutating_executor = std::make_unique<PullingPipelineExecutor>(ctx->projection_mutating_pipeline);
+
             part_merger_writer_task = std::make_unique<PartMergerWriter>(ctx);
         }
     }
@@ -2288,11 +2315,23 @@ bool MutateTask::prepare()
 
         const auto & proj_desc = *(ctx->metadata_snapshot->getProjections().begin());
         const auto & projections_name_and_part = ctx->source_part->getProjectionParts();
-        MergeTreeData::DataPartPtr projection_part = projections_name_and_part.begin()->second;
+        ctx->projection_part = projections_name_and_part.begin()->second;
+
+        MutationCommands projection_commands;
+
+        MutationHelpers::splitAndModifyMutationCommands(
+            ctx->projection_part,
+            proj_desc.metadata,
+            alter_conversions,
+            ctx->commands_for_part,
+            projection_commands,
+            ctx->for_file_renames,
+            false,
+            ctx->log);
 
         auto projection_interpreter = std::make_unique<MutationsInterpreter>(
-            *ctx->data, projection_part, alter_conversions,
-            proj_desc.metadata, ctx->for_interpreter,
+            *ctx->data, ctx->projection_part, alter_conversions,
+            proj_desc.metadata, projection_commands,
             proj_desc.metadata->getColumns().getNamesOfPhysical(), context_for_reading, settings);
 
         ctx->projection_mutating_pipeline_builder = projection_interpreter->execute();
diff --git a/tests/queries/0_stateless/03261_projection_mask.reference b/tests/queries/0_stateless/03261_projection_mask.reference
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/queries/0_stateless/03261_projection_mask.sql b/tests/queries/0_stateless/03261_projection_mask.sql
new file mode 100644
index 00000000000..aeba53700dc
--- /dev/null
+++ b/tests/queries/0_stateless/03261_projection_mask.sql
@@ -0,0 +1,29 @@
+-- compact
+DROP TABLE IF EXISTS users;
+
+CREATE TABLE users (
+    uid Int16,
+    name String,
+    age Int16,
+    projection p1 (select age, count() group by age),
+) ENGINE = MergeTree order by uid
+SETTINGS lightweight_mutation_projection_mode = 'rebuild', min_bytes_for_wide_part = 10485760;
+
+INSERT INTO users VALUES (1231, 'John', 33), (1232, 'Mary', 34);
+
+DELETE FROM users WHERE age = 34;
+
+-- wide
+DROP TABLE IF EXISTS users;
+
+CREATE TABLE users (
+    uid Int16,
+    name String,
+    age Int16,
+    projection p1 (select age, count() group by age),
+) ENGINE = MergeTree order by uid
+SETTINGS lightweight_mutation_projection_mode = 'rebuild', min_bytes_for_wide_part = 0;
+
+INSERT INTO users VALUES (1231, 'John', 33), (1232, 'Mary', 34);
+
+DELETE FROM users WHERE age = 34;