diff --git a/qutebrowser/config/sections.py b/qutebrowser/config/sections.py
index 3a79e42a4..f1ae0b681 100644
--- a/qutebrowser/config/sections.py
+++ b/qutebrowser/config/sections.py
@@ -68,7 +68,7 @@ class Section:
         """Get value keys."""
         return self.values.keys()
 
-    def setv(self, layer, key, value, interpolated):
+    def setv(self, layer, key, value, interpolated=None):
         """Set the value on a layer.
 
         Args:
@@ -111,7 +111,7 @@ class KeyValue(Section):
             self.values[k] = v
             self.descriptions[k] = desc
 
-    def setv(self, layer, key, value, interpolated):
+    def setv(self, layer, key, value, interpolated=None):
         self.values[key].setv(layer, value, interpolated)
 
     def dump_userconfig(self):
@@ -165,7 +165,7 @@ class ValueList(Section):
         self.values = ChainMap(self.layers['temp'], self.layers['conf'],
                                self.layers['default'])
 
-    def setv(self, layer, key, value, interpolated):
+    def setv(self, layer, key, value, interpolated=None):
         self.keytype().validate(key)
         if key in self.layers[layer]:
             self.layers[layer][key].setv(layer, value, interpolated)
diff --git a/qutebrowser/config/value.py b/qutebrowser/config/value.py
index 5a12177c5..11957ecf7 100644
--- a/qutebrowser/config/value.py
+++ b/qutebrowser/config/value.py
@@ -90,7 +90,7 @@ class SettingValue:
         v = self.value
         return self.typ.transform(v)
 
-    def setv(self, layer, value, interpolated):
+    def setv(self, layer, value, interpolated=None):
         """Set the value on a layer.
 
         Args:
@@ -98,6 +98,8 @@ class SettingValue:
                    ValueLayers dict.
             value: The value to set.
             interpolated: The interpolated value, for typechecking.
+                          If None, no checks get performed.
         """
-        self.typ.validate(interpolated)
+        if interpolated is not None:
+            self.typ.validate(interpolated)
         self._values[layer] = value