diff --git a/tests/bugs/core_4964_test.py b/tests/bugs/core_4964_test.py
index 69ea1246..81836d2f 100644
--- a/tests/bugs/core_4964_test.py
+++ b/tests/bugs/core_4964_test.py
@@ -1,140 +1,186 @@
-#coding:utf-8
-
-"""
-ID:          issue-5255
-ISSUE:       5255
-JIRA:        CORE-4964
-FBTEST:      bugs.core_4964
-TITLE:       Real errors during connect to security database are hidden by Srp user manager. Errors should be logged no matter what AuthServer is used
-DESCRIPTION:
-    Test does following:
-    1) creates temporary user using plugin Srp (in order to avoid occasional connect as SYSDBA using Legacy plugin);
-    2) makes copy of test DB to file which is specified n databases.conf as database for alias defined by variable with name REQUIRED_ALIAS
-       (its value: 'tmp_4964_alias'; test will try to connect to this file via ALIAS from pre-created databases.conf);
-    3) uses pre-created databases.conf which has alias and SecurityDatabase parameter in its details.
-       This parameter that points to existing file that for sure can NOT be a Firebird database
-       (file $(dir_conf)/firebird.msg is used for this purpose).
-
-    Then we:
-    1) obtain content of server firebird.log;
-    2) try to make connect to alias <tmp_alias> and (as expected) get error;
-    3) obtain again content of server firebird.log and compare to origin one.
-
-NOTES:
-    [02.08.2022] pzotov
-    1. One need to be sure that firebird.conf does NOT contain DatabaseAccess = None.
-    2. Value of REQUIRED_ALIAS must be EXACTLY the same as alias specified in the pre-created databases.conf
-       (for LINUX this equality is case-sensitive, even when aliases are compared!)
-    3. Make sure that firebird was launched by user who is currently runs this test.
-       Otherwise shutil.copy2() failes with "[Errno 13] Permission denied".
-    4. Content of databases.conf must be taken from $QA_ROOT/files/qa-databases.conf (one need to replace it before every test session).
-       Discussed with pcisar, letters since 30-may-2022 13:48, subject:
-       "new qa, core_4964_test.py: strange outcome when use... shutil.copy() // comparing to shutil.copy2()"
-
-    Checked on 5.0.0.591, 4.0.1.2692, 3.0.8.33535 - both on Windows and Linux.
-"""
-
-import re
-import time
-from pathlib import Path
-from difflib import unified_diff
-
-import pytest
-from firebird.qa import *
-
-substitutions = [('[ \t]+', ' '), ('file .* is not a valid database', 'file is not a valid database'), ]
-
-REQUIRED_ALIAS = 'tmp_core_4964_alias'
-
-db = db_factory()
-act = python_act('db', substitutions=substitutions)
-tmp_user = user_factory('db', name='tmp$c4964', password='123', plugin = 'Srp')
-
-expected_stdout_isql = """
-    Statement failed, SQLSTATE = 08006
-    Error occurred during login, please check server firebird.log for details
-"""
-
-expected_stdout_log_diff = """
-    Authentication error
-    file is not a valid database
-"""
-
-@pytest.mark.version('>=3.0')
-def test_1(act: Action, tmp_user: User, capsys):
-
-    fblog_1 = act.get_firebird_log()
-
-    # Scan line-by-line through databases.conf, find line starting with REQUIRED_ALIAS and extract name of file that
-    # must be created in the $(dir_sampleDb)/qa/ folder. This name will be used further as target database (tmp_fdb).
-    # NOTE: we have to SKIP lines which are commented out, i.e. if they starts with '#':
-    p_required_alias_ptn =  re.compile( '^(?!#)((^|\\s+)' + REQUIRED_ALIAS + ')\\s*=\\s*\\$\\(dir_sampleDb\\)/qa/', re.IGNORECASE )
-    fname_in_dbconf = None
-
-    with open(act.home_dir/'databases.conf', 'r') as f:
-        for line in f:
-            if p_required_alias_ptn.search(line):
-                # If databases.conf contains line like this:
-                #     tmp_4964_alias = $(dir_sampleDb)/qa/tmp_qa_4964.fdb 
-                # - then we extract filename: 'tmp_qa_4964.fdb' (see below):
-                fname_in_dbconf = Path(line.split('=')[1].strip()).name
-                break
-
-    # if 'fname_in_dbconf' remains undefined here then propably REQUIRED_ALIAS not equals to specified in the databases.conf!
-    #
-    assert fname_in_dbconf
-
-    # Full path + filename of database to which we will try to connect:
-    #
-    tmp_fdb = Path( act.vars['sample_dir'], 'qa', fname_in_dbconf )
-    
-    # PermissionError: [Errno 13] Permission denied --> probably because
-    # Firebird was started by root rather than current (non-privileged) user.
-    #
-    tmp_fdb.write_bytes(act.db.db_path.read_bytes())
-
-    check_sql = f'''
-       set bail on;
-       set list on;
-       connect '{act.host+":" if act.host else ""}{tmp_fdb}' user {tmp_user.name} password {tmp_user.password};
-       -- This can occus only if we databases.conf contains {REQUIRED_ALIAS}
-       -- but without reference to invalid security DB (e.g., alias without curly braces at all):
-       select mon$database_name as "UNEXPECTED CONNECTION:" from mon$database;
-       quit;
-    '''
-
-    ###############################################################################################################
-    # POINT-1: check that ISQL raises:
-    # "SQLSTATE = 08006 / Error occurred during login, please check server firebird.log ..."
-    #
-    act.expected_stdout = expected_stdout_isql
-    try:
-        act.isql(switches = ['-q'], input = check_sql, connect_db=False, credentials = False, combine_output = True)
-    finally:
-        tmp_fdb.unlink()
-
-    assert act.clean_stdout == act.clean_expected_stdout
-    act.reset()
-
-    time.sleep(1) # Allow content of firebird log be fully flushed on disk.
-    fblog_2 = act.get_firebird_log()
-
-    diff_patterns = [
-        "\\+\\s+Authentication error",
-        "\\+\\s+file .* is not a valid database",
-    ]
-    diff_patterns = [re.compile(s) for s in diff_patterns]
-    
-    for line in unified_diff(fblog_1, fblog_2):
-        if line.startswith('+'):
-            if act.match_any(line, diff_patterns):
-                print(line.split('+')[-1])
-                
-    ###############################################################################################################
-    # POINT-2: check that diff between firebird.log initial and current content has phrases
-    # 'Authentication error' and '... file is not a valid database':
-    #
-    act.expected_stdout = expected_stdout_log_diff
-    act.stdout = capsys.readouterr().out
-    assert act.clean_stdout == act.clean_expected_stdout
-    act.reset()
+#coding:utf-8
+
+"""
+ID:          issue-5255
+ISSUE:       5255
+JIRA:        CORE-4964
+FBTEST:      bugs.core_4964
+TITLE:       Real errors during connect to security database are hidden by Srp user manager. Errors should be logged no matter what AuthServer is used
+DESCRIPTION:
+    Test does following:
+    1) creates temporary user using plugin Srp (in order to avoid occasional connect as SYSDBA using Legacy plugin);
+    2) makes copy of test DB to file which is specified n databases.conf as database for alias defined by variable with name REQUIRED_ALIAS
+       (its value: 'tmp_4964_alias'; test will try to connect to this file via ALIAS from pre-created databases.conf);
+    3) uses pre-created databases.conf which has alias and SecurityDatabase parameter in its details.
+       This parameter that points to existing file that for sure can NOT be a Firebird database
+       (file $(dir_conf)/firebird.msg is used for this purpose).
+
+    Then we:
+    1) obtain content of server firebird.log;
+    2) try to make connect to alias <tmp_alias> and (as expected) get error;
+    3) obtain again content of server firebird.log and compare to origin one.
+
+NOTES:
+    [02.08.2022] pzotov
+    1. One need to be sure that firebird.conf does NOT contain DatabaseAccess = None.
+    2. Value of REQUIRED_ALIAS must be EXACTLY the same as alias specified in the pre-created databases.conf
+       (for LINUX this equality is case-sensitive, even when aliases are compared!)
+    3. Make sure that firebird was launched by user who is currently runs this test.
+       Otherwise shutil.copy2() failes with "[Errno 13] Permission denied".
+    4. Content of databases.conf must be taken from $QA_ROOT/files/qa-databases.conf (one need to replace it before every test session).
+       Discussed with pcisar, letters since 30-may-2022 13:48, subject:
+       "new qa, core_4964_test.py: strange outcome when use... shutil.copy() // comparing to shutil.copy2()"
+    
+    [31.07.2024] pzotov
+    Replaced assert for ISQL output: added diff_patterns that must filter STDERR because we have to suppress message with text
+    "file ... is not a valid database" as it can be seen only in dev-builds.
+    Expected ISQL output must be compared with filtered capsys.readouterr().out rather than with act.stdout
+    Noted by Dimitry Sibiryakov, https://github.com/FirebirdSQL/firebird-qa/issues/27
+
+    Checked on 5.0.0.591, 4.0.1.2692, 3.0.8.33535 - both on Windows and Linux.
+"""
+
+import re
+import time
+from pathlib import Path
+from difflib import unified_diff
+
+import pytest
+from firebird.qa import *
+
+substitutions = [
+                    ('[ \t]+', ' ')
+                   ,('(-)?file .* is not a valid database', 'file is not a valid database')
+                ]
+
+REQUIRED_ALIAS = 'tmp_core_4964_alias'
+
+db = db_factory()
+act = python_act('db', substitutions = substitutions)
+tmp_user = user_factory('db', name='tmp$c4964', password='123', plugin = 'Srp')
+
+expected_stdout_isql = """
+    Statement failed, SQLSTATE = 08006
+    Error occurred during login, please check server firebird.log for details
+"""
+
+expected_stdout_log_diff = """
+    Authentication error
+    file is not a valid database
+"""
+
+@pytest.mark.version('>=3.0')
+def test_1(act: Action, tmp_user: User, capsys):
+
+    fblog_1 = act.get_firebird_log()
+
+    # Scan line-by-line through databases.conf, find line starting with REQUIRED_ALIAS and extract name of file that
+    # must be created in the $(dir_sampleDb)/qa/ folder. This name will be used further as target database (tmp_fdb).
+    # NOTE: we have to SKIP lines which are commented out, i.e. if they starts with '#':
+    p_required_alias_ptn =  re.compile( '^(?!#)((^|\\s+)' + REQUIRED_ALIAS + ')\\s*=\\s*\\$\\(dir_sampleDb\\)/qa/', re.IGNORECASE )
+    fname_in_dbconf = None
+
+    with open(act.home_dir/'databases.conf', 'r') as f:
+        for line in f:
+            if p_required_alias_ptn.search(line):
+                # If databases.conf contains line like this:
+                #     tmp_4964_alias = $(dir_sampleDb)/qa/tmp_qa_4964.fdb 
+                # - then we extract filename: 'tmp_qa_4964.fdb' (see below):
+                fname_in_dbconf = Path(line.split('=')[1].strip()).name
+                break
+
+    # if 'fname_in_dbconf' remains undefined here then propably REQUIRED_ALIAS not equals to specified in the databases.conf!
+    #
+    assert fname_in_dbconf
+
+    # Full path + filename of database to which we will try to connect:
+    #
+    tmp_fdb = Path( act.vars['sample_dir'], 'qa', fname_in_dbconf )
+    
+    # PermissionError: [Errno 13] Permission denied --> probably because
+    # Firebird was started by root rather than current (non-privileged) user.
+    #
+    tmp_fdb.write_bytes(act.db.db_path.read_bytes())
+
+    check_sql = f'''
+       set bail on;
+       set list on;
+       connect '{act.host+":" if act.host else ""}{tmp_fdb}' user {tmp_user.name} password {tmp_user.password};
+       -- This can occus only if we databases.conf contains {REQUIRED_ALIAS}
+       -- but without reference to invalid security DB (e.g., alias without curly braces at all):
+       select mon$database_name as "UNEXPECTED CONNECTION:" from mon$database;
+       quit;
+    '''
+
+    ###############################################################################################################
+    # POINT-1: check that ISQL raises:
+    # "SQLSTATE = 08006 / Error occurred during login, please check server firebird.log ..."
+    #
+
+    # release build:
+    # ==================================
+    # Statement failed, SQLSTATE = 08006
+    # Error occurred during login, please check server firebird.log for details
+    # ==================================
+
+    # dev-build:
+    # ==================================
+    # Statement failed, SQLSTATE = 08006
+    # Error occurred during login, please check server firebird.log for details
+    # -file ... is not a valid database
+    # ==================================
+    # Last line ("file ... is not a valid database") will be suppressed by substitutions set:
+    #
+
+    isql_err_diff_patterns = [
+         "Statement failed, SQLSTATE = 08006"
+        ,"Error occurred during login, please check server firebird.log for details"
+    ]
+    isql_err_diff_patterns = [re.compile(s) for s in isql_err_diff_patterns]
+    
+    act.expected_stdout = expected_stdout_isql
+    try:
+        act.isql(switches = ['-q'], input = check_sql, connect_db=False, credentials = False, combine_output = True)
+    finally:
+        tmp_fdb.unlink()
+
+    # ::: NB :::
+    # Expected ISQL output must be compared with filtered capsys.readouterr().out rather than with act.stdout
+    for line in act.stdout.splitlines():
+        if act.match_any(line, isql_err_diff_patterns):
+            print(line)
+
+    act.stdout = capsys.readouterr().out
+    assert act.clean_stdout == act.clean_expected_stdout
+    act.reset()
+
+    #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+    time.sleep(1) # Allow content of firebird log be fully flushed on disk.
+    fblog_2 = act.get_firebird_log()
+
+    fb_log_diff_patterns = [
+         "\\+\\s+Authentication error"
+        ,"\\+\\s+file .* is not a valid database"
+    ]
+    fb_log_diff_patterns = [re.compile(s) for s in fb_log_diff_patterns]
+    
+    # BOTH release and dev build will print in firebird.log:
+    # <hostname> <timestamp>
+    # Authentication error
+    # file .* is not a valid database
+    #
+    for line in unified_diff(fblog_1, fblog_2):
+        if line.startswith('+'):
+            if act.match_any(line, fb_log_diff_patterns):
+                print(line.split('+')[-1])
+                
+    ###############################################################################################################
+    # POINT-2: check that diff between firebird.log initial and current content has phrases
+    # 'Authentication error' and '... file is not a valid database':
+    #
+    act.expected_stdout = expected_stdout_log_diff
+    act.stdout = capsys.readouterr().out
+    assert act.clean_stdout == act.clean_expected_stdout
+    act.reset()
+