diff --git a/tests/bugs/core_3509_test.py b/tests/bugs/core_3509_test.py
index f32f7c79..c3b05241 100644
--- a/tests/bugs/core_3509_test.py
+++ b/tests/bugs/core_3509_test.py
@@ -7,6 +7,9 @@ TITLE:       Alter procedure allows to add the parameter with the same name
 DESCRIPTION:
 JIRA:        CORE-3509
 FBTEST:      bugs.core_3509
+NOTES:
+    [30.09.2023] pzotov
+    Expected error message become differ in FB 6.x, added splitting.
 """
 
 import pytest
@@ -39,16 +42,23 @@ test_script = """
 
 act = isql_act('db', test_script)
 
-expected_stderr = """
+expected_stdout_5x = """
     Statement failed, SQLSTATE = 42000
     CREATE OR ALTER PROCEDURE DUPLICATE_OUTPUT_ARGS failed
     -SQL error code = -901
     -duplicate specification of A_DUP - not supported
 """
 
+expected_stdout_6x = """
+    Statement failed, SQLSTATE = 42000
+    CREATE OR ALTER PROCEDURE DUPLICATE_OUTPUT_ARGS failed
+    -Dynamic SQL Error
+    -SQL error code = -637
+    -duplicate specification of A_DUP - not supported
+"""
+
 @pytest.mark.version('>=3.0')
 def test_1(act: Action):
-    act.expected_stderr = expected_stderr
-    act.execute()
-    assert act.clean_stderr == act.clean_expected_stderr
-
+    act.expected_stdout = expected_stdout_5x if act.is_version('<6') else expected_stdout_6x
+    act.execute(combine_output = True)
+    assert act.clean_stdout == act.clean_expected_stdout