diff --git a/src/dsql/BlrDebugWriter.cpp b/src/dsql/BlrDebugWriter.cpp
index f20040fb92..fdb810c440 100644
--- a/src/dsql/BlrDebugWriter.cpp
+++ b/src/dsql/BlrDebugWriter.cpp
@@ -141,13 +141,6 @@ void BlrDebugWriter::putDebugSubProcedure(DeclareSubProcNode* subProcNode)
 	debugData.add(subDebugData.begin(), count);
 }
 
-void BlrDebugWriter::putDebugMarkers(ULONG marks)
-{
-	debugData.add(fb_dbg_map_markers);
-	putValue(marks);
-	putBlrOffset();
-}
-
 void BlrDebugWriter::putValue(ULONG val)
 {
 	debugData.add(val);
diff --git a/src/dsql/BlrDebugWriter.h b/src/dsql/BlrDebugWriter.h
index 41980861ba..ec81544e50 100644
--- a/src/dsql/BlrDebugWriter.h
+++ b/src/dsql/BlrDebugWriter.h
@@ -50,7 +50,6 @@ public:
 	void putDebugCursor(USHORT, const Firebird::MetaName&);
 	void putDebugSubFunction(DeclareSubFuncNode* subFuncNode);
 	void putDebugSubProcedure(DeclareSubProcNode* subProcNode);
-	void putDebugMarkers(ULONG marks);
 
 	DebugData& getDebugData() { return debugData; }
 
diff --git a/src/dsql/DsqlCompilerScratch.cpp b/src/dsql/DsqlCompilerScratch.cpp
index aa5bd71736..a84970b0b8 100644
--- a/src/dsql/DsqlCompilerScratch.cpp
+++ b/src/dsql/DsqlCompilerScratch.cpp
@@ -59,6 +59,27 @@ void DsqlCompilerScratch::dumpContextStack(const DsqlContextStack* stack)
 #endif
 
 
+void DsqlCompilerScratch::putBlrMarkers(ULONG marks)
+{
+	appendUChar(blr_marks);
+	if (marks <= MAX_UCHAR)
+	{
+		appendUChar(1);
+		appendUChar(marks);
+	}
+	else if (marks <= MAX_USHORT)
+	{
+		appendUChar(2);
+		appendUShort(marks);
+	}
+	else
+	{
+		appendUChar(4);
+		appendULong(marks);
+	}
+}
+
+
 // Write out field data type.
 // Taking special care to declare international text.
 void DsqlCompilerScratch::putDtype(const TypeClause* field, bool useSubType)
diff --git a/src/dsql/DsqlCompilerScratch.h b/src/dsql/DsqlCompilerScratch.h
index e54cea0ff1..21b93d731a 100644
--- a/src/dsql/DsqlCompilerScratch.h
+++ b/src/dsql/DsqlCompilerScratch.h
@@ -169,6 +169,7 @@ public:
 		return statement;
 	}
 
+	void putBlrMarkers(ULONG marks);
 	void putDtype(const TypeClause* field, bool useSubType);
 	void putType(const TypeClause* type, bool useSubType);
 	void putLocalVariables(CompoundStmtNode* parameters, USHORT locals);
diff --git a/src/dsql/StmtNodes.cpp b/src/dsql/StmtNodes.cpp
index 61de239c7c..5a60da1189 100644
--- a/src/dsql/StmtNodes.cpp
+++ b/src/dsql/StmtNodes.cpp
@@ -2274,7 +2274,6 @@ static RegisterNode<EraseNode> regEraseNode(blr_erase);
 
 DmlNode* EraseNode::parse(thread_db* /*tdbb*/, MemoryPool& pool, CompilerScratch* csb, const UCHAR /*blrOp*/)
 {
-	const ULONG blrOffset = csb->csb_blr_reader.getOffset();
 	const USHORT n = csb->csb_blr_reader.getByte();
 
 	if (n >= csb->csb_rpt.getCount() || !(csb->csb_rpt[n].csb_flags & csb_used))
@@ -2283,9 +2282,8 @@ DmlNode* EraseNode::parse(thread_db* /*tdbb*/, MemoryPool& pool, CompilerScratch
 	EraseNode* node = FB_NEW_POOL(pool) EraseNode(pool);
 	node->stream = csb->csb_rpt[n].csb_stream;
 
-	ULONG marks;
-	if (csb->csb_dbg_info && csb->csb_dbg_info->blrToMarks.get(blrOffset, marks))
-		node->marks |= marks;
+	if (csb->csb_blr_reader.peekByte() == blr_marks)
+		node->marks |= PAR_marks(csb);
 
 	return node;
 }
@@ -2404,10 +2402,11 @@ void EraseNode::genBlr(DsqlCompilerScratch* dsqlScratch)
 	}
 
 	dsqlScratch->appendUChar(blr_erase);
-	if (marks)
-		dsqlScratch->putDebugMarkers(marks);
 	GEN_stuff_context(dsqlScratch, context);
 
+	if (marks)
+		dsqlScratch->putBlrMarkers(marks);
+
 	if (statement)
 		dsqlScratch->appendUChar(blr_end);
 
@@ -4812,10 +4811,8 @@ DmlNode* ForNode::parse(thread_db* tdbb, MemoryPool& pool, CompilerScratch* csb,
 {
 	ForNode* node = FB_NEW_POOL(pool) ForNode(pool);
 
-	const ULONG blrOffset = csb->csb_blr_reader.getOffset();
-	ULONG marks;
-	if (csb->csb_dbg_info && csb->csb_dbg_info->blrToMarks.get(blrOffset, marks))
-		node->forUpdate = (marks & StmtNode::MARK_FOR_UPDATE) != 0;
+	if (csb->csb_blr_reader.peekByte() == blr_marks)
+		node->forUpdate = (PAR_marks(csb) & StmtNode::MARK_FOR_UPDATE) != 0;
 
 	if (csb->csb_blr_reader.peekByte() == (UCHAR) blr_stall)
 		node->stall = PAR_parse_stmt(tdbb, csb);
@@ -4932,7 +4929,7 @@ void ForNode::genBlr(DsqlCompilerScratch* dsqlScratch)
 	dsqlScratch->appendUChar(blr_for);
 
 	if (forUpdate)
-		dsqlScratch->putDebugMarkers(StmtNode::MARK_FOR_UPDATE);
+		dsqlScratch->putBlrMarkers(StmtNode::MARK_FOR_UPDATE);
 
 	if (!statement || dsqlForceSingular)
 		dsqlScratch->appendUChar(blr_singular);
@@ -5970,8 +5967,6 @@ static RegisterNode<ModifyNode> regModifyNode2(blr_modify2);
 DmlNode* ModifyNode::parse(thread_db* tdbb, MemoryPool& pool, CompilerScratch* csb, const UCHAR blrOp)
 {
 	// Parse the original and new contexts.
-	const ULONG blrOffset = csb->csb_blr_reader.getOffset();
-
 	USHORT context = (unsigned int) csb->csb_blr_reader.getByte();
 
 	if (context >= csb->csb_rpt.getCount() || !(csb->csb_rpt[context].csb_flags & csb_used))
@@ -6000,6 +5995,9 @@ DmlNode* ModifyNode::parse(thread_db* tdbb, MemoryPool& pool, CompilerScratch* c
 	node->orgStream = orgStream;
 	node->newStream = newStream;
 
+	if (csb->csb_blr_reader.peekByte() == blr_marks)
+		node->marks |= PAR_marks(csb);
+
 	AutoSetRestore<StmtNode*> autoCurrentDMLNode(&csb->csb_currentDMLNode, node);
 
 	node->statement = PAR_parse_stmt(tdbb, csb);
@@ -6007,10 +6005,6 @@ DmlNode* ModifyNode::parse(thread_db* tdbb, MemoryPool& pool, CompilerScratch* c
 	if (blrOp == blr_modify2)
 		node->statement2 = PAR_parse_stmt(tdbb, csb);
 
-	ULONG marks;
-	if (csb->csb_dbg_info && csb->csb_dbg_info->blrToMarks.get(blrOffset, marks))
-		node->marks |= marks;
-
 	return node;
 }
 
@@ -6239,8 +6233,6 @@ void ModifyNode::genBlr(DsqlCompilerScratch* dsqlScratch)
 	const dsql_msg* message = dsqlGenDmlHeader(dsqlScratch, rse);
 
 	dsqlScratch->appendUChar(statement2 ? blr_modify2 : blr_modify);
-	if (marks)
-		dsqlScratch->putDebugMarkers(marks);
 
 	const dsql_ctx* context;
 
@@ -6255,6 +6247,10 @@ void ModifyNode::genBlr(DsqlCompilerScratch* dsqlScratch)
 	GEN_stuff_context(dsqlScratch, context);
 	context = dsqlRelation->dsqlContext;
 	GEN_stuff_context(dsqlScratch, context);
+
+	if (marks)
+		dsqlScratch->putBlrMarkers(marks);
+
 	statement->genBlr(dsqlScratch);
 
 	if (statement2)
@@ -8913,7 +8909,7 @@ static const dsql_msg* dsqlGenDmlHeader(DsqlCompilerScratch* dsqlScratch, RseNod
 	if (dsqlRse)
 	{
 		dsqlScratch->appendUChar(blr_for);
-		dsqlScratch->putDebugMarkers(StmtNode::MARK_FOR_UPDATE);
+		dsqlScratch->putBlrMarkers(StmtNode::MARK_FOR_UPDATE);
 		GEN_expr(dsqlScratch, dsqlRse);
 	}
 
diff --git a/src/include/firebird/impl/blr.h b/src/include/firebird/impl/blr.h
index 70a41ac159..b75354c8c6 100644
--- a/src/include/firebird/impl/blr.h
+++ b/src/include/firebird/impl/blr.h
@@ -441,4 +441,6 @@
 #define blr_at_local				(unsigned char) 0
 #define blr_at_zone					(unsigned char) 1
 
+#define blr_marks					(unsigned char) 217		// mark some blr code with specific flags
+
 #endif // FIREBIRD_IMPL_BLR_H
diff --git a/src/include/firebird/impl/consts_pub.h b/src/include/firebird/impl/consts_pub.h
index 74be2b75bb..9ba14d70f9 100644
--- a/src/include/firebird/impl/consts_pub.h
+++ b/src/include/firebird/impl/consts_pub.h
@@ -740,7 +740,6 @@
 #define fb_dbg_subproc				5
 #define fb_dbg_subfunc				6
 #define fb_dbg_map_curname			7
-#define fb_dbg_map_markers			8
 
 // sub code for fb_dbg_map_argument
 #define fb_dbg_arg_input			0
diff --git a/src/jrd/DebugInterface.cpp b/src/jrd/DebugInterface.cpp
index d0e528e8b1..79de9e8147 100644
--- a/src/jrd/DebugInterface.cpp
+++ b/src/jrd/DebugInterface.cpp
@@ -225,28 +225,6 @@ void DBG_parse_debug_info(ULONG length, const UCHAR* data, DbgInfo& dbgInfo)
 				break;
 			}
 
-		case fb_dbg_map_markers:
-			{
-				if (data + 8 >= end)
-				{
-					bad_format = true;
-					break;
-				}
-
-				ULONG marks = *data++;
-				marks |= *data++ << 8;
-				marks |= *data++ << 16;
-				marks |= *data++ << 24;
-
-				ULONG offset = *data++;
-				offset |= *data++ << 8;
-				offset |= *data++ << 16;
-				offset |= *data++ << 24;
-
-				dbgInfo.blrToMarks.put(offset, marks);
-			}
-			break;
-
 		case fb_dbg_end:
 			if (data != end)
 				bad_format = true;
diff --git a/src/jrd/DebugInterface.h b/src/jrd/DebugInterface.h
index b7f3836e5c..f7cd7253f9 100644
--- a/src/jrd/DebugInterface.h
+++ b/src/jrd/DebugInterface.h
@@ -33,8 +33,7 @@
 // Also, it introduces some new tags.
 const UCHAR DBG_INFO_VERSION_1 = UCHAR(1);
 const UCHAR DBG_INFO_VERSION_2 = UCHAR(2);
-const UCHAR DBG_INFO_VERSION_3 = UCHAR(3);	// blr offsets of "update" cursors and driven sub-statements
-const UCHAR CURRENT_DBG_INFO_VERSION = DBG_INFO_VERSION_3;
+const UCHAR CURRENT_DBG_INFO_VERSION = DBG_INFO_VERSION_2;
 
 namespace Firebird {
 
@@ -56,7 +55,6 @@ typedef Firebird::SortedArray<
 	MapBlrToSrcItem> MapBlrToSrc;
 
 typedef GenericMap<Pair<Right<USHORT, MetaName> > > MapVarIndexToName;
-typedef GenericMap<Pair<NonPooled<ULONG, ULONG> > > MapBlrToMarks;
 
 struct ArgumentInfo
 {
@@ -95,8 +93,7 @@ struct DbgInfo : public PermanentStorage
 		  argInfoToName(p),
 		  curIndexToName(p),
 		  subFuncs(p),
-		  subProcs(p),
-		  blrToMarks(p)
+		  subProcs(p)
 	{
 	}
 
@@ -129,8 +126,6 @@ struct DbgInfo : public PermanentStorage
 
 			subProcs.clear();
 		}
-
-		blrToMarks.clear();
 	}
 
 	MapBlrToSrc blrToSrc;					// mapping between blr offsets and source text position
@@ -139,7 +134,6 @@ struct DbgInfo : public PermanentStorage
 	MapVarIndexToName curIndexToName;		// mapping between cursor index and name
 	GenericMap<Pair<Left<MetaName, DbgInfo*> > > subFuncs;	// sub functions
 	GenericMap<Pair<Left<MetaName, DbgInfo*> > > subProcs;	// sub procedures
-	MapBlrToMarks blrToMarks;				// blr offsets of marked verbs
 };
 
 } // namespace Firebird
diff --git a/src/jrd/blp.h b/src/jrd/blp.h
index da41ec60aa..a6e41a55b0 100644
--- a/src/jrd/blp.h
+++ b/src/jrd/blp.h
@@ -247,5 +247,6 @@ static const struct
 	{"local_timestamp", byte_line},
 	{"local_time", byte_line},
 	{"at", verb_byte_verb},
+	{"marks", byte_literal},
 	{0, 0}
 };
diff --git a/src/jrd/par.cpp b/src/jrd/par.cpp
index 951cdeec40..99b1027ae6 100644
--- a/src/jrd/par.cpp
+++ b/src/jrd/par.cpp
@@ -683,6 +683,26 @@ CompoundStmtNode* PAR_make_list(thread_db* tdbb, StmtNodeStack& stack)
 }
 
 
+ULONG PAR_marks(Jrd::CompilerScratch* csb)
+{
+	if (csb->csb_blr_reader.getByte() != blr_marks)
+		PAR_syntax_error(csb, "blr_marks");
+
+	switch (csb->csb_blr_reader.getByte())
+	{
+	case 1:
+		return csb->csb_blr_reader.getByte();
+
+	case 2:
+		return csb->csb_blr_reader.getWord();
+
+	case 4:
+		return csb->csb_blr_reader.getLong();
+	}
+	PAR_syntax_error(csb, "valid length for blr_marks value (1, 2, or 4)");
+	return 0;
+}
+
 CompilerScratch* PAR_parse(thread_db* tdbb, const UCHAR* blr, ULONG blr_length,
 	bool internal_flag, ULONG dbginfo_length, const UCHAR* dbginfo)
 {
@@ -1627,6 +1647,7 @@ void PAR_syntax_error(CompilerScratch* csb, const TEXT* string)
 
 	csb->csb_blr_reader.seekBackward(1);
 
+	// BLR syntax error: expected @1 at offset @2, encountered @3
 	PAR_error(csb, Arg::Gds(isc_syntaxerr) << Arg::Str(string) <<
 										  Arg::Num(csb->csb_blr_reader.getOffset()) <<
 										  Arg::Num(csb->csb_blr_reader.peekByte()));
diff --git a/src/jrd/par_proto.h b/src/jrd/par_proto.h
index 487f8dfe8b..13a5c8594c 100644
--- a/src/jrd/par_proto.h
+++ b/src/jrd/par_proto.h
@@ -61,6 +61,7 @@ SSHORT			PAR_find_proc_field(const Jrd::jrd_prc*, const Firebird::MetaName&);
 Jrd::ValueExprNode* PAR_gen_field(Jrd::thread_db* tdbb, StreamType stream, USHORT id, bool byId = false);
 Jrd::ValueExprNode* PAR_make_field(Jrd::thread_db*, Jrd::CompilerScratch*, USHORT, const Firebird::MetaName&);
 Jrd::CompoundStmtNode*	PAR_make_list(Jrd::thread_db*, Jrd::StmtNodeStack&);
+ULONG			PAR_marks(Jrd::CompilerScratch*);
 Jrd::CompilerScratch*	PAR_parse(Jrd::thread_db*, const UCHAR* blr, ULONG blr_length,
 	bool internal_flag, ULONG = 0, const UCHAR* = NULL);