diff --git a/apollo-federation/src/query_plan/fetch_dependency_graph.rs b/apollo-federation/src/query_plan/fetch_dependency_graph.rs
index 1b6bedb55b..d1360120c7 100644
--- a/apollo-federation/src/query_plan/fetch_dependency_graph.rs
+++ b/apollo-federation/src/query_plan/fetch_dependency_graph.rs
@@ -729,6 +729,7 @@ impl FetchDependencyGraph {
 
     /// Adds another node as a parent of `child`,
     /// meaning that this fetch should happen after the provided one.
+    /// Assumption: The parent node is not a descendant of the child.
     fn add_parent(&mut self, child_id: NodeIndex, parent_relation: ParentRelation) {
         let ParentRelation {
             parent_node_id,
@@ -738,8 +739,8 @@ impl FetchDependencyGraph {
             return;
         }
         assert!(
-            !self.graph.contains_edge(child_id, parent_node_id),
-            "Node {parent_node_id:?} is a child of {child_id:?}: \
+            !self.is_descendant_of(parent_node_id, child_id),
+            "Node {parent_node_id:?} is a descendant of {child_id:?}: \
              adding it as parent would create a cycle"
         );
         self.on_modification();
@@ -794,15 +795,7 @@ impl FetchDependencyGraph {
     }
 
     fn is_descendant_of(&self, node_id: NodeIndex, maybe_ancestor_id: NodeIndex) -> bool {
-        if node_id == maybe_ancestor_id {
-            return true;
-        }
-        for child_id in self.children_of(node_id) {
-            if self.is_descendant_of(child_id, maybe_ancestor_id) {
-                return true;
-            }
-        }
-        false
+        petgraph::algo::has_path_connecting(&self.graph, maybe_ancestor_id, node_id, None)
     }
 
     /// Returns whether `node_id` is both a child of `maybe_parent_id` but also if we can show that the