diff --git a/src/library/tactic/unfold_tactic.cpp b/src/library/tactic/unfold_tactic.cpp
index f9a2cb1f40..8ac7ebd7c9 100644
--- a/src/library/tactic/unfold_tactic.cpp
+++ b/src/library/tactic/unfold_tactic.cpp
@@ -335,7 +335,7 @@ class unfold_rec_fn : public replace_visitor_aux {
         expr const new_head = get_app_fn(new_e);
         // TODO(Leo): create an option for the following conditions?
         if (is_constant(new_head) && inductive::is_elim_rule(m_env, const_name(new_head))) {
-            //head is a recursor... so the unfold is probably not generating a nice result...
+            // head is a recursor... so the unfold is probably not generating a nice result...
             throw fold_failed();
         }
         return fold_rec_fn(m_ctx, fn, args, k, rec_name, indices_pos, main_pos, rec_arg_pos)(new_e);