diff --git a/compiler/mono/src/decision_tree.rs b/compiler/mono/src/decision_tree.rs
index d949172117..c033449cb0 100644
--- a/compiler/mono/src/decision_tree.rs
+++ b/compiler/mono/src/decision_tree.rs
@@ -419,7 +419,6 @@ fn gather_edges<'a>(
 
     let check = guarded_tests_are_complete(&relevant_tests);
 
-    // TODO remove clone
     let all_edges = relevant_tests
         .into_iter()
         .map(|t| edges_for(path, &branches, t))
@@ -1055,9 +1054,19 @@ fn small_defaults(branches: &[Branch], path: &[PathInstruction]) -> usize {
 }
 
 fn small_branching_factor(branches: &[Branch], path: &[PathInstruction]) -> usize {
-    let (edges, fallback) = gather_edges(branches.to_vec(), path);
+    // a specialized version of gather_edges that just counts the number of options
 
-    edges.len() + (if fallback.is_empty() { 0 } else { 1 })
+    let relevant_tests = tests_at_path(path, branches);
+
+    let check = guarded_tests_are_complete(&relevant_tests);
+
+    let fallbacks = if check {
+        false
+    } else {
+        branches.iter().any(|b| is_irrelevant_to(path, b))
+    };
+
+    relevant_tests.len() + (if !fallbacks { 0 } else { 1 })
 }
 
 #[derive(Clone, Debug, PartialEq)]