diff --git a/hugr-passes/src/call_graph.rs b/hugr-passes/src/call_graph.rs
index 47f56a695..13a83f4e1 100644
--- a/hugr-passes/src/call_graph.rs
+++ b/hugr-passes/src/call_graph.rs
@@ -77,31 +77,24 @@ impl CallGraph {
 fn reachable_funcs<'a>(
     cg: &'a CallGraph,
     h: &impl HugrView,
-    roots: impl IntoIterator<Item = Node>,
+    entry_points: impl IntoIterator<Item = Node>,
 ) -> impl Iterator<Item = Node> + 'a {
-    let mut entry_points = roots.into_iter().collect_vec();
+    let mut roots = entry_points.into_iter().collect_vec();
     let mut b = if h.get_optype(h.root()).is_module() {
-        if entry_points.is_empty() {
-            entry_points.push(
-                h.children(h.root())
-                    .filter(|n| {
-                        h.get_optype(*n)
-                            .as_func_defn()
-                            .is_some_and(|fd| fd.name == "main")
-                    })
-                    .exactly_one()
-                    .ok()
-                    .expect("No entry_points provided, Module must contain `main`"),
-            );
+        if roots.is_empty() {
+            roots.extend(h.children(h.root()).filter(|n| {
+                h.get_optype(*n)
+                    .as_func_defn()
+                    .is_some_and(|fd| fd.name == "main")
+            }));
+            assert!(!roots.is_empty(), "No entry_points for Module and no `main`");
         }
-        let mut entry_points = entry_points
-            .into_iter()
-            .map(|i| cg.node_to_g.get(&i).unwrap());
-        let mut b = Bfs::new(&cg.g, *entry_points.next().unwrap());
-        b.stack.extend(entry_points);
+        let mut roots = roots.into_iter().map(|i| cg.node_to_g.get(&i).unwrap());
+        let mut b = Bfs::new(&cg.g, *roots.next().unwrap());
+        b.stack.extend(roots);
         b
     } else {
-        assert!(entry_points.is_empty());
+        assert!(roots.is_empty());
         Bfs::new(&cg.g, *cg.node_to_g.get(&h.root()).unwrap())
     };
     std::iter::from_fn(move || b.next(&cg.g)).map(|i| *cg.g.node_weight(i).unwrap())