diff --git a/src/Storages/MergeTree/IMergeTreeDataPart.cpp b/src/Storages/MergeTree/IMergeTreeDataPart.cpp
index a1565173b47..a20e5fc7264 100644
--- a/src/Storages/MergeTree/IMergeTreeDataPart.cpp
+++ b/src/Storages/MergeTree/IMergeTreeDataPart.cpp
@@ -807,7 +807,7 @@ MergeTreeDataPartBuilder IMergeTreeDataPart::getProjectionPartBuilder(const Stri
     const char * projection_extension = is_temp_projection ? ".tmp_proj" : ".proj";
     auto projection_storage = getDataPartStorage().getProjection(projection_name + projection_extension, !is_temp_projection);
     MergeTreeDataPartBuilder builder(storage, projection_name, projection_storage);
-    return builder.withPartInfo({"all", 0, 0, 0}).withParentPart(this);
+    return builder.withPartInfo(MergeListElement::FAKE_RESULT_PART_FOR_PROJECTION).withParentPart(this);
 }
 
 void IMergeTreeDataPart::addProjectionPart(
diff --git a/src/Storages/MergeTree/MergeList.cpp b/src/Storages/MergeTree/MergeList.cpp
index 8fbb163384e..b80d7fccc91 100644
--- a/src/Storages/MergeTree/MergeList.cpp
+++ b/src/Storages/MergeTree/MergeList.cpp
@@ -6,10 +6,18 @@
 #include <Common/CurrentThread.h>
 #include <Common/MemoryTracker.h>
 
+#include <Common/logger_useful.h>
 
 namespace DB
 {
 
+namespace ErrorCodes
+{
+    extern const int LOGICAL_ERROR;
+}
+
+const MergeTreePartInfo MergeListElement::FAKE_RESULT_PART_FOR_PROJECTION = {"all", 0, 0, 0};
+
 MergeListElement::MergeListElement(const StorageID & table_id_, FutureMergedMutatedPartPtr future_part, const ContextPtr & context)
     : table_id{table_id_}
     , partition_id{future_part->part_info.partition_id}
@@ -21,8 +29,23 @@ MergeListElement::MergeListElement(const StorageID & table_id_, FutureMergedMuta
     , merge_type{future_part->merge_type}
     , merge_algorithm{MergeAlgorithm::Undecided}
 {
+    auto format_version = MERGE_TREE_DATA_MIN_FORMAT_VERSION_WITH_CUSTOM_PARTITIONING;
+    if (result_part_name != result_part_info.getPartNameV1())
+        format_version = MERGE_TREE_DATA_OLD_FORMAT_VERSION;
+
+    /// FIXME why do we need a merge list element for projection parts at all?
+    bool is_fake_projection_part = future_part->part_info == FAKE_RESULT_PART_FOR_PROJECTION;
+
+    size_t normal_parts_count = 0;
     for (const auto & source_part : future_part->parts)
     {
+        if (!is_fake_projection_part && !source_part->getParentPart())
+        {
+            ++normal_parts_count;
+            if (!result_part_info.contains(MergeTreePartInfo::fromPartName(source_part->name, format_version)))
+                throw Exception(ErrorCodes::LOGICAL_ERROR, "Source part {} is not covered by result part {}", source_part->name, result_part_info.getPartNameV1());
+        }
+
         source_part_names.emplace_back(source_part->name);
         source_part_paths.emplace_back(source_part->getDataPartStorage().getFullPath());
 
@@ -35,13 +58,17 @@ MergeListElement::MergeListElement(const StorageID & table_id_, FutureMergedMuta
     if (!future_part->parts.empty())
     {
         source_data_version = future_part->parts[0]->info.getDataVersion();
-        is_mutation = (result_part_info.getDataVersion() != source_data_version);
+        is_mutation = (result_part_info.level == future_part->parts[0]->info.level) && !is_fake_projection_part;
 
         WriteBufferFromString out(partition);
         const auto & part = future_part->parts[0];
         part->partition.serializeText(part->storage, out, {});
     }
 
+    if (!is_fake_projection_part && is_mutation && normal_parts_count != 1)
+        throw Exception(ErrorCodes::LOGICAL_ERROR, "Got {} source parts for mutation {}: {}", future_part->parts.size(),
+                        result_part_info.getPartNameV1(), fmt::join(source_part_names, ", "));
+
     thread_group = ThreadGroup::createForBackgroundProcess(context);
 }
 
diff --git a/src/Storages/MergeTree/MergeList.h b/src/Storages/MergeTree/MergeList.h
index d40af6abf43..66190de0ef4 100644
--- a/src/Storages/MergeTree/MergeList.h
+++ b/src/Storages/MergeTree/MergeList.h
@@ -66,6 +66,8 @@ struct Settings;
 
 struct MergeListElement : boost::noncopyable
 {
+    static const MergeTreePartInfo FAKE_RESULT_PART_FOR_PROJECTION;
+
     const StorageID table_id;
     std::string partition_id;
     std::string partition;
diff --git a/src/Storages/MergeTree/MergeTask.cpp b/src/Storages/MergeTree/MergeTask.cpp
index aa178be270f..fa86bb31629 100644
--- a/src/Storages/MergeTree/MergeTask.cpp
+++ b/src/Storages/MergeTree/MergeTask.cpp
@@ -1021,7 +1021,7 @@ bool MergeTask::MergeProjectionsStage::mergeMinMaxIndexAndPrepareProjections() c
         // TODO (ab): path in future_part is only for merge process introspection, which is not available for merges of projection parts.
         // Let's comment this out to avoid code inconsistency and add it back after we implement projection merge introspection.
         // projection_future_part->path = global_ctx->future_part->path + "/" + projection.name + ".proj/";
-        projection_future_part->part_info = {"all", 0, 0, 0};
+        projection_future_part->part_info = MergeListElement::FAKE_RESULT_PART_FOR_PROJECTION;
 
         MergeTreeData::MergingParams projection_merging_params;
         projection_merging_params.mode = MergeTreeData::MergingParams::Ordinary;