diff --git a/src/Storages/MergeTree/MergeTask.cpp b/src/Storages/MergeTree/MergeTask.cpp
index 9fe16ad8650..56bd1181fef 100644
--- a/src/Storages/MergeTree/MergeTask.cpp
+++ b/src/Storages/MergeTree/MergeTask.cpp
@@ -818,11 +818,6 @@ bool MergeTask::MergeProjectionsStage::mergeMinMaxIndexAndPrepareProjections() c
         // projection_future_part->path = global_ctx->future_part->path + "/" + projection.name + ".proj/";
         projection_future_part->part_info = {"all", 0, 0, 0};
 
-        Names deduplicate_by_columns;
-        for (const auto & column : global_ctx->deduplicate_by_columns)
-            if (projection.metadata->getColumns().has(column))
-                deduplicate_by_columns.emplace_back(column);
-
         MergeTreeData::MergingParams projection_merging_params;
         projection_merging_params.mode = MergeTreeData::MergingParams::Ordinary;
         if (projection.type == ProjectionDescription::Type::Aggregate)
@@ -837,7 +832,7 @@ bool MergeTask::MergeProjectionsStage::mergeMinMaxIndexAndPrepareProjections() c
             global_ctx->context,
             global_ctx->space_reservation,
             global_ctx->deduplicate,
-            deduplicate_by_columns,
+            global_ctx->deduplicate_by_columns,
             global_ctx->cleanup,
             projection_merging_params,
             global_ctx->need_prefix,
diff --git a/src/Storages/StorageMergeTree.cpp b/src/Storages/StorageMergeTree.cpp
index 9352f772ce1..0dd0f051244 100644
--- a/src/Storages/StorageMergeTree.cpp
+++ b/src/Storages/StorageMergeTree.cpp
@@ -1549,6 +1549,12 @@ bool StorageMergeTree::optimize(
 {
     assertNotReadonly();
 
+    if (deduplicate && getInMemoryMetadataPtr()->hasProjections())
+        throw Exception(ErrorCodes::NOT_IMPLEMENTED,
+                    "OPTIMIZE DEDUPLICATE query is not supported for table {} as it has projections. "
+                    "User should drop all the projections manually before running the query",
+                    getStorageID().getTableName());
+
     if (deduplicate)
     {
         if (deduplicate_by_columns.empty())
diff --git a/src/Storages/StorageReplicatedMergeTree.cpp b/src/Storages/StorageReplicatedMergeTree.cpp
index db58d0081c6..403313a7177 100644
--- a/src/Storages/StorageReplicatedMergeTree.cpp
+++ b/src/Storages/StorageReplicatedMergeTree.cpp
@@ -5746,6 +5746,12 @@ bool StorageReplicatedMergeTree::optimize(
     if (!is_leader)
         throw Exception(ErrorCodes::NOT_A_LEADER, "OPTIMIZE cannot be done on this replica because it is not a leader");
 
+    if (deduplicate && getInMemoryMetadataPtr()->hasProjections())
+        throw Exception(ErrorCodes::NOT_IMPLEMENTED,
+                    "OPTIMIZE DEDUPLICATE query is not supported for table {} as it has projections. "
+                    "User should drop all the projections manually before running the query",
+                    getStorageID().getTableName());
+
     if (cleanup)
     {
         if (!getSettings()->allow_experimental_replacing_merge_with_cleanup)
diff --git a/tests/queries/0_stateless/03174_projection_deduplicate.reference b/tests/queries/0_stateless/03174_projection_deduplicate.reference
index d2ee9d25154..586b63a392e 100644
--- a/tests/queries/0_stateless/03174_projection_deduplicate.reference
+++ b/tests/queries/0_stateless/03174_projection_deduplicate.reference
@@ -1 +1,2 @@
 1	one
+1	one
diff --git a/tests/queries/0_stateless/03174_projection_deduplicate.sql b/tests/queries/0_stateless/03174_projection_deduplicate.sql
index 529c3260baa..ed6da5d73fc 100644
--- a/tests/queries/0_stateless/03174_projection_deduplicate.sql
+++ b/tests/queries/0_stateless/03174_projection_deduplicate.sql
@@ -17,7 +17,7 @@ PRIMARY KEY id;
 INSERT INTO test_projection_deduplicate VALUES (1, 'one');
 INSERT INTO test_projection_deduplicate VALUES (1, 'one');
 
-OPTIMIZE TABLE test_projection_deduplicate DEDUPLICATE;
+OPTIMIZE TABLE test_projection_deduplicate DEDUPLICATE; -- { serverError NOT_IMPLEMENTED }
 
 SELECT * FROM test_projection_deduplicate;