diff --git a/src/common/classes/TriState.h b/src/common/classes/TriState.h
index 08347d0aea3..6c481dfc6e1 100644
--- a/src/common/classes/TriState.h
+++ b/src/common/classes/TriState.h
@@ -29,6 +29,7 @@
 #ifndef CLASSES_TRISTATE_H
 #define CLASSES_TRISTATE_H
 
+namespace Firebird {
 
 class TriState
 {
@@ -129,5 +130,6 @@ inline bool TriState::toggle()
 	return true;
 }
 
+} // namespace Firebird
 
 #endif // CLASSES_TRISTATE_H
diff --git a/src/dsql/DdlNodes.h b/src/dsql/DdlNodes.h
index 2cdc276c250..aa8ca427c40 100644
--- a/src/dsql/DdlNodes.h
+++ b/src/dsql/DdlNodes.h
@@ -482,7 +482,7 @@ class CreateAlterFunctionNode : public DdlNode
 	bool privateScope;
 	bool preserveDefaults;
 	SLONG udfReturnPos;
-	TriState ssDefiner;
+	Firebird::TriState ssDefiner;
 };
 
 
@@ -616,7 +616,7 @@ class CreateAlterProcedureNode : public DdlNode
 	MetaName packageOwner;
 	bool privateScope;
 	bool preserveDefaults;
-	TriState ssDefiner;
+	Firebird::TriState ssDefiner;
 };
 
 
@@ -700,7 +700,7 @@ class TriggerDefinition
 	MetaName name;
 	MetaName relationName;
 	std::optional<FB_UINT64> type;
-	TriState active;
+	Firebird::TriState active;
 	std::optional<int> position;
 	NestConst<ExternalClause> external;
 	Firebird::string source;
@@ -990,7 +990,7 @@ class AlterDomainNode : public DdlNode
 	NestConst<ValueSourceClause> setDefault;
 	MetaName renameTo;
 	Firebird::AutoPtr<dsql_fld> type;
-	TriState notNullFlag;	// true = NOT NULL / false = NULL
+	Firebird::TriState notNullFlag;	// true = NOT NULL / false = NULL
 };
 
 
@@ -1214,7 +1214,7 @@ class RelationNode : public DdlNode
 		MetaName identitySequence;
 		std::optional<IdentityType> identityType;
 		std::optional<USHORT> collationId;
-		TriState notNullFlag;	// true = NOT NULL / false = NULL
+		Firebird::TriState notNullFlag;	// true = NOT NULL / false = NULL
 		std::optional<USHORT> position;
 		Firebird::string defaultSource;
 		Firebird::ByteChunk defaultValue;
@@ -1553,8 +1553,8 @@ class RelationNode : public DdlNode
 	NestConst<RelationSourceNode> dsqlNode;
 	MetaName name;
 	Firebird::Array<NestConst<Clause> > clauses;
-	TriState ssDefiner;
-	TriState replicationState;
+	Firebird::TriState ssDefiner;
+	Firebird::TriState replicationState;
 };
 
 
@@ -1726,9 +1726,9 @@ class CreateIndexNode : public DdlNode
 
 		MetaName relation;
 		Firebird::ObjectsArray<MetaName> columns;
-		TriState unique;
-		TriState descending;
-		TriState inactive;
+		Firebird::TriState unique;
+		Firebird::TriState descending;
+		Firebird::TriState inactive;
 		SSHORT type;
 		bid expressionBlr;
 		bid expressionSource;
@@ -2219,8 +2219,8 @@ class CreateAlterUserNode : public UserNode
 	Firebird::string* lastName;
 	MetaName* plugin;
 	Firebird::string* comment;
-	TriState adminRole;
-	TriState active;
+	Firebird::TriState adminRole;
+	Firebird::TriState active;
 	Mode mode;
 
 	void addProperty(MetaName* pr, Firebird::string* val = NULL)
@@ -2461,7 +2461,7 @@ class AlterDatabaseNode : public DdlNode
 	Firebird::Array<NestConst<DbFileClause> > files;
 	MetaName cryptPlugin;
 	MetaName keyName;
-	TriState ssDefiner;
+	Firebird::TriState ssDefiner;
 	Firebird::Array<MetaName> pubTables;
 };
 
diff --git a/src/dsql/NodePrinter.h b/src/dsql/NodePrinter.h
index 271993d17e8..4caa8fedc9c 100644
--- a/src/dsql/NodePrinter.h
+++ b/src/dsql/NodePrinter.h
@@ -267,7 +267,7 @@ class NodePrinter
 			print(s, *array);
 	}
 
-	void print(const Firebird::string& s, const TriState& triState)
+	void print(const Firebird::string& s, const Firebird::TriState& triState)
 	{
 		if (triState.isAssigned())
 			print(s, triState.asBool());
diff --git a/src/dsql/PackageNodes.h b/src/dsql/PackageNodes.h
index 0e1ad83d2b2..7c68ec011cd 100644
--- a/src/dsql/PackageNodes.h
+++ b/src/dsql/PackageNodes.h
@@ -110,7 +110,7 @@ class CreateAlterPackageNode : public DdlNode
 	Firebird::Array<Item>* items;
 	Firebird::SortedArray<MetaName> functionNames;
 	Firebird::SortedArray<MetaName> procedureNames;
-	TriState ssDefiner;
+	Firebird::TriState ssDefiner;
 
 private:
 	MetaName owner;
diff --git a/src/dsql/Parser.h b/src/dsql/Parser.h
index 229b8132f55..77e0b2ac04d 100644
--- a/src/dsql/Parser.h
+++ b/src/dsql/Parser.h
@@ -261,13 +261,13 @@ class Parser : public Firebird::PermanentStorage
 		}
 	}
 
-	void setClause(TriState& clause, const char* duplicateMsg, bool value)
+	void setClause(Firebird::TriState& clause, const char* duplicateMsg, bool value)
 	{
 		checkDuplicateClause(clause, duplicateMsg);
 		clause = value;
 	}
 
-	void setClause(TriState& clause, const char* duplicateMsg, const TriState& value)
+	void setClause(Firebird::TriState& clause, const char* duplicateMsg, const Firebird::TriState& value)
 	{
 		if (value.isAssigned())
 		{
@@ -322,7 +322,7 @@ class Parser : public Firebird::PermanentStorage
 		return clause.hasData();
 	}
 
-	bool isDuplicateClause(const TriState& clause)
+	bool isDuplicateClause(const Firebird::TriState& clause)
 	{
 		return clause.isAssigned();
 	}
diff --git a/src/dsql/StmtNodes.h b/src/dsql/StmtNodes.h
index 6976fd81035..fee771dfc81 100644
--- a/src/dsql/StmtNodes.h
+++ b/src/dsql/StmtNodes.h
@@ -1340,7 +1340,7 @@ class SelectNode final : public TypedNode<DsqlOnlyStmtNode, StmtNode::TYPE_SELEC
 public:
 	NestConst<SelectExprNode> selectExpr;
 	NestConst<RseNode> rse;
-	TriState optimizeForFirstRows;
+	Firebird::TriState optimizeForFirstRows;
 	bool forUpdate = false;
 	bool withLock = false;
 	bool skipLocked = false;
@@ -1626,12 +1626,12 @@ class SetTransactionNode : public TransactionNode
 	std::optional<CommitNumber> atSnapshotNumber;
 	std::optional<unsigned> isoLevel;
 	std::optional<USHORT> lockTimeout;
-	TriState readOnly;
-	TriState wait;
-	TriState noAutoUndo;
-	TriState ignoreLimbo;
-	TriState restartRequests;
-	TriState autoCommit;
+	Firebird::TriState readOnly;
+	Firebird::TriState wait;
+	Firebird::TriState noAutoUndo;
+	Firebird::TriState ignoreLimbo;
+	Firebird::TriState restartRequests;
+	Firebird::TriState autoCommit;
 };
 
 
@@ -1901,7 +1901,7 @@ class SetOptimizeNode : public SessionManagementNode
 	virtual void execute(thread_db* tdbb, DsqlRequest* request, jrd_tra** traHandle) const;
 
 public:
-	TriState optimizeMode;
+	Firebird::TriState optimizeMode;
 };
 
 
diff --git a/src/dsql/parse.y b/src/dsql/parse.y
index 58df2a5cf0c..a40f513fe3f 100644
--- a/src/dsql/parse.y
+++ b/src/dsql/parse.y
@@ -736,7 +736,7 @@ using namespace Firebird;
 	{}
 
 	std::optional<int> nullableIntVal;
-	TriState triState;
+	Firebird::TriState triState;
 	std::optional<Jrd::TriggerDefinition::SqlSecurity> nullableSqlSecurityVal;
 	std::optional<Jrd::OverrideClause> nullableOverrideClause;
 	struct { bool first; bool second; } boolPair;
diff --git a/src/jrd/Attachment.h b/src/jrd/Attachment.h
index 29f3752f4f5..1df3287a151 100644
--- a/src/jrd/Attachment.h
+++ b/src/jrd/Attachment.h
@@ -640,7 +640,7 @@ class Attachment : public pool_alloc<type_att>
 	USHORT att_original_timezone;
 	USHORT att_current_timezone;
 	int att_parallel_workers;
-	TriState att_opt_first_rows;
+	Firebird::TriState att_opt_first_rows;
 
 	PageToBufferMap* att_bdb_cache;			// managed in CCH, created in att_pool, freed with it
 
diff --git a/src/jrd/Database.h b/src/jrd/Database.h
index 1f7d5073dc1..ae780fa56bd 100644
--- a/src/jrd/Database.h
+++ b/src/jrd/Database.h
@@ -532,7 +532,7 @@ class Database : public pool_alloc<type_dbb>
 	time_t dbb_linger_end;
 	Firebird::RefPtr<Firebird::IPluginConfig> dbb_plugin_config;
 
-	TriState dbb_repl_state;			// replication state
+	Firebird::TriState dbb_repl_state;	// replication state
 	Lock* dbb_repl_lock;				// replication state lock
 	Firebird::SyncObject dbb_repl_sync;
 	FB_UINT64 dbb_repl_sequence;		// replication sequence
diff --git a/src/jrd/RecordSourceNodes.h b/src/jrd/RecordSourceNodes.h
index b64b3afcbb7..65ee4ed7e0a 100644
--- a/src/jrd/RecordSourceNodes.h
+++ b/src/jrd/RecordSourceNodes.h
@@ -878,7 +878,7 @@ class RseNode final : public TypedNode<RecordSourceNode, RecordSourceNode::TYPE_
 	Firebird::Array<NestConst<RecordSourceNode> > rse_relations;
 	USHORT flags = 0;
 	USHORT rse_jointype = blr_inner;	// inner, left, full
-	TriState firstRows;					// optimize for first rows
+	Firebird::TriState firstRows;					// optimize for first rows
 };
 
 class SelectExprNode final : public TypedNode<RecordSourceNode, RecordSourceNode::TYPE_SELECT_EXPR>
diff --git a/src/jrd/Relation.h b/src/jrd/Relation.h
index ab721d5bc25..5445b60c4ef 100644
--- a/src/jrd/Relation.h
+++ b/src/jrd/Relation.h
@@ -264,9 +264,9 @@ class jrd_rel : public pool_alloc<type_rel>
 	TrigVector*	rel_post_store;			// Post-operation store trigger
 	prim		rel_primary_dpnds;		// foreign dependencies on this relation's primary key
 	frgn		rel_foreign_refs;		// foreign references to other relations' primary keys
-	TriState	rel_ss_definer;
 
-	TriState	rel_repl_state;			// replication state
+	Firebird::TriState	rel_ss_definer;
+	Firebird::TriState	rel_repl_state;			// replication state
 
 	Firebird::Mutex rel_drop_mutex;
 
diff --git a/src/jrd/jrd.h b/src/jrd/jrd.h
index d5a17f3558c..250239e0cf2 100644
--- a/src/jrd/jrd.h
+++ b/src/jrd/jrd.h
@@ -148,7 +148,7 @@ class Trigger
 	Firebird::string	entryPoint;			// External trigger entrypoint
 	Firebird::string	extBody;			// External trigger body
 	ExtEngineManager::Trigger* extTrigger;	// External trigger
-	TriState ssDefiner;
+	Firebird::TriState ssDefiner;
 	MetaName	owner;				// Owner for SQL SECURITY
 
 	bool isActive() const;
diff --git a/src/jrd/met_proto.h b/src/jrd/met_proto.h
index 6e4b9849123..35534208d2e 100644
--- a/src/jrd/met_proto.h
+++ b/src/jrd/met_proto.h
@@ -148,6 +148,6 @@ void MET_store_dependencies(Jrd::thread_db*, Firebird::Array<Jrd::CompilerScratc
 	const Jrd::jrd_rel*, const Jrd::MetaName&, int, Jrd::jrd_tra*);
 
 int			MET_get_linger(Jrd::thread_db*);
-TriState	MET_get_ss_definer(Jrd::thread_db*);
+Firebird::TriState	MET_get_ss_definer(Jrd::thread_db*);
 
 #endif // JRD_MET_PROTO_H
diff --git a/src/jrd/val.h b/src/jrd/val.h
index c7e79654c01..c0056fa9406 100644
--- a/src/jrd/val.h
+++ b/src/jrd/val.h
@@ -31,7 +31,6 @@
 
 #include "../include/fb_blk.h"
 #include "../common/classes/array.h"
-#include "../common/classes/TriState.h"
 #include "../jrd/intl_classes.h"
 #include "../jrd/MetaName.h"
 #include "../jrd/QualifiedName.h"