diff --git a/test/functional/interface_rpc.py b/test/functional/interface_rpc.py
index 46dbd2f809d..d9636c122ad 100755
--- a/test/functional/interface_rpc.py
+++ b/test/functional/interface_rpc.py
@@ -8,10 +8,9 @@ import json
 import os
 from dataclasses import dataclass
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal, assert_greater_than_or_equal
+from test_framework.util import JSONRPCException, assert_equal, assert_greater_than_or_equal
 from threading import Thread
 from typing import Optional
-import subprocess
 
 
 RPC_INVALID_PARAMETER      = -8
@@ -83,8 +82,8 @@ def test_work_queue_getblock(node, got_exceeded_error):
     while not got_exceeded_error:
         try:
             node.cli("waitfornewblock", "500").send_cli()
-        except subprocess.CalledProcessError as e:
-            assert_equal(e.output, 'error: Server response: Work queue depth exceeded\n')
+        except JSONRPCException as e:
+            assert_equal(e.error["message"], "non-JSON HTTP response with '503 Service Unavailable' from server: Work queue depth exceeded")
             got_exceeded_error.append(True)
 
 
diff --git a/test/functional/test_framework/test_node.py b/test/functional/test_framework/test_node.py
index 24c76564862..0308c5466b8 100755
--- a/test/functional/test_framework/test_node.py
+++ b/test/functional/test_framework/test_node.py
@@ -967,6 +967,13 @@ class TestNodeCLI():
             if match:
                 code, message = match.groups()
                 raise JSONRPCException(dict(code=int(code), message=message))
+            match = re.match(r'error: Server response: (.*)\n?$', cli_stderr)
+            if match:
+                message = match.group(1)
+                raise JSONRPCException(dict(
+                    code=-342,
+                    message=f"non-JSON HTTP response with '503 Service Unavailable' from server: {message}",
+                ), http_status=503)
             # Ignore cli_stdout, raise with cli_stderr
             raise subprocess.CalledProcessError(returncode, p_args, output=cli_stderr)
         try: