diff --git a/src/solver/parallel_tactical2.h b/src/solver/parallel_tactical2.h
index 1fbab40bc..b27a4c740 100644
--- a/src/solver/parallel_tactical2.h
+++ b/src/solver/parallel_tactical2.h
@@ -20,6 +20,6 @@ Author:
 
 class tactic;
 class solver;
-struct params_ref;
+class params_ref;
 
 tactic * mk_parallel_tactic2(solver* s, params_ref const& p);