diff --git a/src/dsql/Parser.cpp b/src/dsql/Parser.cpp
index bd81726647..c2a9fd465e 100644
--- a/src/dsql/Parser.cpp
+++ b/src/dsql/Parser.cpp
@@ -37,7 +37,7 @@ Parser::Parser(MemoryPool& pool, USHORT aClientDialect, USHORT aDbDialect, USHOR
 	  db_dialect(aDbDialect),
 	  parser_version(aParserVersion),
 	  transformedString(pool),
-	  introducerMarks(pool),
+	  strMarks(pool),
 	  stmt_ambiguous(false)
 {
 	yyps = 0;
@@ -112,15 +112,22 @@ void Parser::transformString(const char* start, unsigned length, string& dest)
 	HalfStaticArray<char, 256> buffer;
 	const char* pos = start;
 
-	for (size_t i = 0; i < introducerMarks.getCount(); ++i)
+	// We need only the "introduced" strings, in the bounds of "start" and "length" and in "pos"
+	// order. Let collect them.
+
+	SortedArray<StrMark> introducedMarks;
+
+	GenericMap<NonPooled<dsql_str*, StrMark> >::ConstAccessor accessor(&strMarks);
+	for (bool found = accessor.getFirst(); found; found = accessor.getNext())
 	{
-		const IntroducerMark& mark = introducerMarks[i];
+		const StrMark& mark = accessor.current()->second;
+		if (mark.introduced && mark.pos >= fromBegin && mark.pos < fromBegin + length)
+			introducedMarks.add(mark);
+	}
 
-		if (mark.pos < fromBegin)
-			continue;
-
-		if (mark.pos >= fromBegin + length)
-			break;
+	for (size_t i = 0; i < introducedMarks.getCount(); ++i)
+	{
+		const StrMark& mark = introducedMarks[i];
 
 		const char* s = lex.start + mark.pos;
 		buffer.add(pos, s - pos);
diff --git a/src/dsql/Parser.h b/src/dsql/Parser.h
index 22afde6c75..f9602d88d3 100644
--- a/src/dsql/Parser.h
+++ b/src/dsql/Parser.h
@@ -91,8 +91,22 @@ private:
 		USHORT param_number;
 	};
 
-	struct IntroducerMark
+	struct StrMark
 	{
+		StrMark()
+			: introduced(false),
+			  pos(0),
+			  length(0),
+			  str(NULL)
+		{
+		}
+
+		bool operator >(const StrMark& o) const
+		{
+			return pos > o.pos;
+		}
+
+		bool introduced;
 		unsigned pos;
 		unsigned length;
 		dsql_str* str;
@@ -156,7 +170,7 @@ private:
 	USHORT parser_version;
 
 	Firebird::string transformedString;
-	Firebird::Array<IntroducerMark> introducerMarks;
+	Firebird::GenericMap<Firebird::NonPooled<dsql_str*, StrMark> > strMarks;
 	bool stmt_ambiguous;
 	dsql_nod* DSQL_parse;
 
diff --git a/src/dsql/parse.y b/src/dsql/parse.y
index 580c7ab20c..fe81f799f8 100644
--- a/src/dsql/parse.y
+++ b/src/dsql/parse.y
@@ -5131,12 +5131,10 @@ sql_string
 			str->str_charset = $1;
 			if (str->type == dsql_str::TYPE_SIMPLE || str->type == dsql_str::TYPE_ALTERNATE)
 			{
-				IntroducerMark mark;
-				mark.pos = lex.last_token - lex.start;
-				mark.length = lex.ptr - lex.last_token;
-				mark.str = str;
-
-				introducerMarks.push(mark);
+				StrMark* mark = strMarks.get(str);
+				fb_assert(mark);
+				if (mark)
+					mark->introduced = true;
 			}
 			$$ = str;
 		}
@@ -6432,6 +6430,9 @@ int Parser::yylexAux()
 
 	if (tok_class & CHR_QUOTE)
 	{
+		StrMark mark;
+		mark.pos = lex.last_token - lex.start;
+
 		char* buffer = string;
 		size_t buffer_len = sizeof (string);
 		const char* buffer_end = buffer + buffer_len - 1;
@@ -6519,6 +6520,11 @@ int Parser::yylexAux()
 		yylval.legacyStr = MAKE_string(buffer, p - buffer);
 		if (buffer != string)
 			gds__free (buffer);
+
+		mark.length = lex.ptr - lex.last_token;
+		mark.str = yylval.legacyStr;
+		strMarks.put(mark.str, mark);
+
 		return STRING;
 	}
 
@@ -6655,6 +6661,9 @@ int Parser::yylexAux()
 
 	if ((c == 'q' || c == 'Q') && lex.ptr + 3 < lex.end && *lex.ptr == '\'')
 	{
+		StrMark mark;
+		mark.pos = lex.last_token - lex.start;
+
 		char endChar = *++lex.ptr;
 		switch (endChar)
 		{
@@ -6679,6 +6688,11 @@ int Parser::yylexAux()
 				yylval.legacyStr = MAKE_string(lex.last_token + 3, lex.ptr - lex.last_token - 4);
 				yylval.legacyStr->type = dsql_str::TYPE_ALTERNATE;
 				lex.ptr++;
+
+				mark.length = lex.ptr - lex.last_token;
+				mark.str = yylval.legacyStr;
+				strMarks.put(mark.str, mark);
+
 				return STRING;
 			}
 		}