diff --git a/rust/hg-core/src/discovery.rs b/rust/hg-core/src/discovery.rs
--- a/rust/hg-core/src/discovery.rs
+++ b/rust/hg-core/src/discovery.rs
@@ -266,7 +266,7 @@
 
         self.mutate_undecided(
             |oc| oc.compute_undecided(),
-            |wu| wu.add_missing_revisions(missing),
+            |wu| Ok(wu.add_missing_revisions(missing)),
         )
     }
 
@@ -456,10 +456,7 @@
     /// caller from `PartialDiscovery` can avoid the undecided set in case
     /// it turns out to be empty (hence restrain
     /// from performing the transition to `WithUndecided`)
-    pub fn add_missing_revisions(
-        &mut self,
-        mut tovisit: VecDeque<Revision>,
-    ) -> Result<(), GraphError> {
+    pub fn add_missing_revisions(&mut self, mut tovisit: VecDeque<Revision>) {
         let mut seen: HashSet<Revision> = HashSet::new();
         let undecided_mut = &mut self.undecided;
         let children = &self.children_cache;
@@ -473,20 +470,14 @@
                 continue;
             }
             undecided_mut.remove(&rev);
-            match children.get(&rev) {
-                None => {
-                    continue;
-                }
-                Some(this_children) => {
-                    for child in this_children.iter().cloned() {
-                        if seen.insert(child) {
-                            tovisit.push_back(child);
-                        }
+            if let Some(this_children) = children.get(&rev) {
+                for child in this_children.iter().cloned() {
+                    if seen.insert(child) {
+                        tovisit.push_back(child);
                     }
                 }
             }
         }
-        Ok(())
     }
 
     fn compute_children_cache(