diff --git a/pylsp/plugins/flake8_lint.py b/pylsp/plugins/flake8_lint.py
index 8d8d4c5f..77aa22b9 100644
--- a/pylsp/plugins/flake8_lint.py
+++ b/pylsp/plugins/flake8_lint.py
@@ -9,9 +9,13 @@
 from pathlib import PurePath
 from subprocess import PIPE, Popen
 
+from flake8.plugins.pyflakes import FLAKE8_PYFLAKES_CODES
+
 from pylsp import hookimpl, lsp
+from pylsp.plugins.pyflakes_lint import PYFLAKES_ERROR_MESSAGES
 
 log = logging.getLogger(__name__)
+
 FIX_IGNORES_RE = re.compile(r"([^a-zA-Z0-9_,]*;.*(\W+||$))")
 UNNECESSITY_CODES = {
     "F401",  # `module` imported but unused
@@ -20,6 +24,14 @@
     "F523",  # .format(...) unused positional arguments
     "F841",  # local variable `name` is assigned to but never used
 }
+# NOTE: If the user sets the flake8 executable with workspace configuration, the
+# error codes in this set may be inaccurate.
+ERROR_CODES = (
+    # Errors from the pyflakes plugin of flake8
+    {FLAKE8_PYFLAKES_CODES.get(m.__name__, "E999") for m in PYFLAKES_ERROR_MESSAGES}
+    # Syntax error from flake8 itself
+    | {"E999"}
+)
 
 
 @hookimpl
@@ -208,7 +220,7 @@ def parse_stdout(source, stdout):
         # show also the code in message
         msg = code + " " + msg
         severity = lsp.DiagnosticSeverity.Warning
-        if code == "E999" or code[0] == "F":
+        if code in ERROR_CODES:
             severity = lsp.DiagnosticSeverity.Error
         diagnostic = {
             "source": "flake8",
diff --git a/test/plugins/test_flake8_lint.py b/test/plugins/test_flake8_lint.py
index 882bc996..c2d711e7 100644
--- a/test/plugins/test_flake8_lint.py
+++ b/test/plugins/test_flake8_lint.py
@@ -40,7 +40,7 @@ def test_flake8_unsaved(workspace):
     assert unused_var["code"] == "F841"
     assert unused_var["range"]["start"] == {"line": 5, "character": 1}
     assert unused_var["range"]["end"] == {"line": 5, "character": 11}
-    assert unused_var["severity"] == lsp.DiagnosticSeverity.Error
+    assert unused_var["severity"] == lsp.DiagnosticSeverity.Warning
     assert unused_var["tags"] == [lsp.DiagnosticTag.Unnecessary]
 
 
@@ -55,7 +55,7 @@ def test_flake8_lint(workspace):
         assert unused_var["code"] == "F841"
         assert unused_var["range"]["start"] == {"line": 5, "character": 1}
         assert unused_var["range"]["end"] == {"line": 5, "character": 11}
-        assert unused_var["severity"] == lsp.DiagnosticSeverity.Error
+        assert unused_var["severity"] == lsp.DiagnosticSeverity.Warning
     finally:
         os.remove(name)
 
@@ -101,7 +101,7 @@ def test_flake8_respecting_configuration(workspace):
                 "end": {"line": 5, "character": 11},
             },
             "message": "F841 local variable 'a' is assigned to but never used",
-            "severity": 1,
+            "severity": 2,
             "tags": [1],
         },
     ]
@@ -116,7 +116,7 @@ def test_flake8_respecting_configuration(workspace):
                 "end": {"line": 0, "character": 9},
             },
             "message": "F401 'os' imported but unused",
-            "severity": 1,
+            "severity": 2,
             "tags": [1],
         }
     ]