diff --git a/src/autorouter/autorouter.rs b/src/autorouter/autorouter.rs
index a62dc1e..d94b750 100644
--- a/src/autorouter/autorouter.rs
+++ b/src/autorouter/autorouter.rs
@@ -176,16 +176,13 @@ impl<M: AccessMesadata> Autorouter<M> {
     }
 
     pub fn measure_length(
-        &mut self,
+        &self,
         selection: &BandSelection,
     ) -> Result<MeasureLengthExecutionStepper, AutorouterError> {
         MeasureLengthExecutionStepper::new(selection)
     }
 
-    pub fn ratline_endpoints(
-        &mut self,
-        ratline: EdgeIndex<usize>,
-    ) -> (FixedDotIndex, FixedDotIndex) {
+    pub fn ratline_endpoints(&self, ratline: EdgeIndex<usize>) -> (FixedDotIndex, FixedDotIndex) {
         let (source, target) = self.ratsnest.graph().edge_endpoints(ratline).unwrap();
 
         let source_dot = match self
diff --git a/src/autorouter/measure_length.rs b/src/autorouter/measure_length.rs
index 5e60fa9..07425eb 100644
--- a/src/autorouter/measure_length.rs
+++ b/src/autorouter/measure_length.rs
@@ -35,7 +35,7 @@ impl MeasureLengthExecutionStepper {
 
     pub fn doit(
         &mut self,
-        autorouter: &mut Autorouter<impl AccessMesadata>,
+        autorouter: &Autorouter<impl AccessMesadata>,
     ) -> Result<f64, AutorouterError> {
         let length = if let Some(length) = self.maybe_length {
             length