diff --git a/qutebrowser/config/configfiles.py b/qutebrowser/config/configfiles.py
index e26a03454..a155726a8 100644
--- a/qutebrowser/config/configfiles.py
+++ b/qutebrowser/config/configfiles.py
@@ -30,7 +30,7 @@ import yaml
 from PyQt5.QtCore import QSettings
 
 import qutebrowser
-from qutebrowser.config import configexc, config
+from qutebrowser.config import configexc, config, configdata
 from qutebrowser.utils import standarddir, utils, qtutils
 
 
@@ -153,6 +153,12 @@ class YamlConfig:
                 "'global' object is not a dict")
             raise configexc.ConfigFileErrors('autoconfig.yml', [desc])
 
+        # Delete unknown values
+        # (e.g. options which were removed from configdata.yml)
+        for name in list(global_obj):
+            if name not in configdata.DATA:
+                del global_obj[name]
+
         self._values = global_obj
         self._dirty = False
 
diff --git a/tests/unit/config/test_config.py b/tests/unit/config/test_config.py
index 6dff3c30a..36dc90c10 100644
--- a/tests/unit/config/test_config.py
+++ b/tests/unit/config/test_config.py
@@ -932,14 +932,9 @@ def test_early_init(init_patch, config_tmpdir, caplog, fake_args,
         expected_errors.append(
             "Errors occurred while reading config.py:\n"
             "  While setting 'foo': No option 'foo'")
-    if invalid_yaml and (load_autoconfig or not config_py):
+    if invalid_yaml == '42' and (load_autoconfig or not config_py):
         error = "Errors occurred while reading autoconfig.yml:\n"
-        if invalid_yaml == '42':
-            error += "  While loading data: Toplevel object is not a dict"
-        elif invalid_yaml == 'unknown':
-            error += "  Error: No option 'colors.foobar'"
-        else:
-            assert False, invalid_yaml
+        error += "  While loading data: Toplevel object is not a dict"
         expected_errors.append(error)
 
     actual_errors = [str(err) for err in config._init_errors]
diff --git a/tests/unit/config/test_configfiles.py b/tests/unit/config/test_configfiles.py
index 219b92395..fdfda4033 100644
--- a/tests/unit/config/test_configfiles.py
+++ b/tests/unit/config/test_configfiles.py
@@ -57,6 +57,8 @@ def test_state_config(fake_save_manager, data_tmpdir,
 @pytest.mark.parametrize('old_config', [
     None,
     'global:\n  colors.hints.fg: magenta',
+    # Unknown key
+    'global:\n  hello: world',
 ])
 @pytest.mark.parametrize('insert', [True, False])
 def test_yaml_config(fake_save_manager, config_tmpdir, old_config, insert):
@@ -91,6 +93,7 @@ def test_yaml_config(fake_save_manager, config_tmpdir, old_config, insert):
         assert '  colors.hints.fg: magenta' in lines
     if insert:
         assert '  tabs.show: never' in lines
+    assert '  hello:' not in lines
 
 
 @pytest.mark.parametrize('old_config', [