diff --git a/src/Dictionaries/DictionaryFactory.h b/src/Dictionaries/DictionaryFactory.h
index 0dc80af62fc..309f14f6b7f 100644
--- a/src/Dictionaries/DictionaryFactory.h
+++ b/src/Dictionaries/DictionaryFactory.h
@@ -54,6 +54,9 @@ public:
         bool created_from_ddl)>;
 
     bool isComplex(const std::string & layout_type) const;
+
+    /// if the argument `layout_type` is not complex layout and has corresponding complex layout,
+    /// change `layout_type` to corresponding complex and return true; otherwise do nothing and return false.
     bool convertToComplex(std::string & layout_type) const;
 
     void registerLayout(const std::string & layout_type, LayoutCreateFunction create_layout, bool is_layout_complex, bool has_layout_complex = true);
diff --git a/tests/queries/0_stateless/02731_auto_convert_dictionary_layout_to_complex_by_complex_keys.reference b/tests/queries/0_stateless/02731_auto_convert_dictionary_layout_to_complex_by_complex_keys.reference
new file mode 100644
index 00000000000..7f38556e7d1
--- /dev/null
+++ b/tests/queries/0_stateless/02731_auto_convert_dictionary_layout_to_complex_by_complex_keys.reference
@@ -0,0 +1,4 @@
+dict_flat_simple	Flat
+dict_hashed_simple	Hashed
+dict_hashed_complex	ComplexKeyHashed
+dict_hashed_simple_auto_convert	ComplexKeyHashed
diff --git a/tests/queries/0_stateless/02731_auto_convert_dictionary_layout_to_complex_by_complex_keys.sql b/tests/queries/0_stateless/02731_auto_convert_dictionary_layout_to_complex_by_complex_keys.sql
new file mode 100644
index 00000000000..98c7c5c05f9
--- /dev/null
+++ b/tests/queries/0_stateless/02731_auto_convert_dictionary_layout_to_complex_by_complex_keys.sql
@@ -0,0 +1,29 @@
+DROP DICTIONARY IF EXISTS dict_flat_simple;
+DROP DICTIONARY IF EXISTS dict_hashed_simple;
+DROP DICTIONARY IF EXISTS dict_hashed_complex;
+DROP DICTIONARY IF EXISTS dict_hashed_simple_auto_convert;
+DROP TABLE IF EXISTS dict_data;
+
+CREATE TABLE dict_data (v0 UInt16, v1 UInt16, v2 UInt16, v3 UInt16, v4 UInt16) engine=Memory() AS SELECT number, number%65535, number%65535, number%6553, number%655355 FROM numbers(100);
+
+CREATE DICTIONARY dict_flat_simple (v0 UInt16, v1 UInt16, v2 UInt16) PRIMARY KEY v0 SOURCE(CLICKHOUSE(TABLE 'dict_data')) LIFETIME(0) LAYOUT(flat());
+SYSTEM RELOAD DICTIONARY dict_flat_simple;
+SELECT name, type FROM system.dictionaries WHERE database = currentDatabase() AND name = 'dict_flat_simple';
+DROP DICTIONARY dict_flat_simple;
+
+CREATE DICTIONARY dict_hashed_simple (v0 UInt16, v1 UInt16, v2 UInt16) PRIMARY KEY v0 SOURCE(CLICKHOUSE(TABLE 'dict_data')) LIFETIME(0) LAYOUT(hashed());
+SYSTEM RELOAD DICTIONARY dict_hashed_simple;
+SELECT name, type FROM system.dictionaries WHERE database = currentDatabase() AND name = 'dict_hashed_simple';
+DROP DICTIONARY dict_hashed_simple;
+
+CREATE DICTIONARY dict_hashed_complex (v0 UInt16, v1 UInt16, v2 UInt16) PRIMARY KEY v0,v1 SOURCE(CLICKHOUSE(TABLE 'dict_data')) LIFETIME(0) LAYOUT(complex_key_hashed());
+SYSTEM RELOAD DICTIONARY dict_hashed_complex;
+SELECT name, type FROM system.dictionaries WHERE database = currentDatabase() AND name = 'dict_hashed_complex';
+DROP DICTIONARY dict_hashed_complex;
+
+CREATE DICTIONARY dict_hashed_simple_auto_convert (v0 UInt16, v1 UInt16, v2 UInt16) PRIMARY KEY v0,v1 SOURCE(CLICKHOUSE(TABLE 'dict_data')) LIFETIME(0) LAYOUT(hashed());
+SYSTEM RELOAD DICTIONARY dict_hashed_simple_auto_convert;
+SELECT name, type FROM system.dictionaries WHERE database = currentDatabase() AND name = 'dict_hashed_simple_auto_convert';
+DROP DICTIONARY dict_hashed_simple_auto_convert;
+
+DROP TABLE dict_data;