diff --git a/mitmproxy/optmanager.py b/mitmproxy/optmanager.py
index a8720f79a..190faabb9 100644
--- a/mitmproxy/optmanager.py
+++ b/mitmproxy/optmanager.py
@@ -434,7 +434,7 @@ class OptManager:
             raise ValueError("Unsupported option type: %s", o.typespec)
 
 
-def dump_defaults(opts):
+def dump_defaults(opts, out: typing.TextIO):
     """
         Dumps an annotated file with all options.
     """
@@ -453,7 +453,7 @@ def dump_defaults(opts):
 
         txt = "\n".join(textwrap.wrap(txt))
         s.yaml_set_comment_before_after_key(k, before="\n" + txt)
-    return ruamel.yaml.round_trip_dump(s)
+    return ruamel.yaml.YAML().dump(s, out)
 
 
 def dump_dicts(opts, keys: typing.List[str]=None):
@@ -482,7 +482,8 @@ def parse(text):
     if not text:
         return {}
     try:
-        data = ruamel.yaml.load(text, ruamel.yaml.RoundTripLoader)
+        yaml = ruamel.yaml.YAML(typ='unsafe', pure=True)
+        data = yaml.load(text)
     except ruamel.yaml.error.YAMLError as v:
         if hasattr(v, "problem_mark"):
             snip = v.problem_mark.get_snippet()
@@ -532,7 +533,7 @@ def load_paths(opts: OptManager, *paths: str) -> None:
                 )
 
 
-def serialize(opts: OptManager, text: str, defaults: bool = False) -> str:
+def serialize(opts: OptManager, file: typing.TextIO, text: str, defaults: bool = False) -> None:
     """
         Performs a round-trip serialization. If text is not None, it is
         treated as a previous serialization that should be modified
@@ -550,9 +551,8 @@ def serialize(opts: OptManager, text: str, defaults: bool = False) -> str:
     for k in list(data.keys()):
         if k not in opts._options:
             del data[k]
-    ret = ruamel.yaml.round_trip_dump(data)
-    assert ret
-    return ret
+
+    ruamel.yaml.YAML().dump(data, file)
 
 
 def save(opts: OptManager, path: str, defaults: bool =False) -> None:
@@ -572,6 +572,6 @@ def save(opts: OptManager, path: str, defaults: bool =False) -> None:
                 )
     else:
         data = ""
-    data = serialize(opts, data, defaults)
+
     with open(path, "wt", encoding="utf8") as f:
-        f.write(data)
+        serialize(opts, f, data, defaults)
diff --git a/mitmproxy/tools/console/keymap.py b/mitmproxy/tools/console/keymap.py
index d15853157..1ba7c9bd1 100644
--- a/mitmproxy/tools/console/keymap.py
+++ b/mitmproxy/tools/console/keymap.py
@@ -2,6 +2,7 @@ import typing
 import os
 
 import ruamel.yaml
+import ruamel.yaml.error
 
 from mitmproxy import command
 from mitmproxy.tools.console import commandexecutor
@@ -217,8 +218,8 @@ class KeymapConfig:
 
     def parse(self, text):
         try:
-            data = ruamel.yaml.safe_load(text)
-        except ruamel.yaml.error.YAMLError as v:
+            data = ruamel.yaml.YAML(typ='safe', pure=True).load(text)
+        except ruamel.yaml.error.MarkedYAMLError as v:
             if hasattr(v, "problem_mark"):
                 snip = v.problem_mark.get_snippet()
                 raise KeyBindingError(
@@ -230,7 +231,7 @@ class KeymapConfig:
         if not data:
             return []
         if not isinstance(data, list):
-            raise KeyBindingError("Inalid keybinding config - expected a list of keys")
+            raise KeyBindingError("Invalid keybinding config - expected a list of keys")
 
         for k in data:
             unknown = k.keys() - keyAttrs.keys()
diff --git a/mitmproxy/tools/main.py b/mitmproxy/tools/main.py
index ba0e8bf8e..60923d5b8 100644
--- a/mitmproxy/tools/main.py
+++ b/mitmproxy/tools/main.py
@@ -85,7 +85,7 @@ def run(
         process_options(parser, opts, args)
 
         if args.options:
-            print(optmanager.dump_defaults(opts))
+            optmanager.dump_defaults(opts, sys.stdout)
             sys.exit(0)
         if args.commands:
             master.commands.dump()
diff --git a/setup.py b/setup.py
index 92a6c34a8..10df7d30f 100644
--- a/setup.py
+++ b/setup.py
@@ -84,7 +84,7 @@ setup(
         "pyOpenSSL>=20.0,<20.1",
         "pyparsing>=2.4.2,<2.5",
         "pyperclip>=1.6.0,<1.9",
-        "ruamel.yaml>=0.16,<0.17",
+        "ruamel.yaml>=0.16,<0.17.9",
         "sortedcontainers>=2.3,<2.5",
         "tornado>=4.3,<7",
         "urwid>=2.1.1,<2.2",
diff --git a/test/mitmproxy/test_optmanager.py b/test/mitmproxy/test_optmanager.py
index 9d109c229..fe8b59746 100644
--- a/test/mitmproxy/test_optmanager.py
+++ b/test/mitmproxy/test_optmanager.py
@@ -1,4 +1,5 @@
 import copy
+import io
 import pytest
 import typing
 import argparse
@@ -239,11 +240,16 @@ def test_items():
 
 
 def test_serialize():
+    def serialize(opts: optmanager.OptManager, text: str, defaults: bool = False) -> str:
+        buf = io.StringIO()
+        optmanager.serialize(opts, buf, text, defaults)
+        return buf.getvalue()
+
     o = TD2()
     o.three = "set"
-    assert "dfour" in optmanager.serialize(o, None, defaults=True)
+    assert "dfour" in serialize(o, "", defaults=True)
 
-    data = optmanager.serialize(o, None)
+    data = serialize(o, "")
     assert "dfour" not in data
 
     o2 = TD2()
@@ -254,7 +260,7 @@ def test_serialize():
     t = """
         unknown: foo
     """
-    data = optmanager.serialize(o, t)
+    data = serialize(o, t)
     o2 = TD2()
     optmanager.load(o2, data)
     assert o2 == o
@@ -280,7 +286,9 @@ def test_serialize():
 
 def test_serialize_defaults():
     o = options.Options()
-    assert optmanager.serialize(o, None, defaults=True)
+    buf = io.StringIO()
+    optmanager.serialize(o, buf, "", defaults=True)
+    assert buf.getvalue()
 
 
 def test_saving(tmpdir):
@@ -348,7 +356,9 @@ def test_option():
 
 def test_dump_defaults():
     o = TTypes()
-    assert optmanager.dump_defaults(o)
+    buf = io.StringIO()
+    optmanager.dump_defaults(o, buf)
+    assert buf.getvalue()
 
 
 def test_dump_dicts():