diff --git a/src/goto-symex/memory_model_pso.cpp b/src/goto-symex/memory_model_pso.cpp
index 2ef634e208c..d8487e629fd 100644
--- a/src/goto-symex/memory_model_pso.cpp
+++ b/src/goto-symex/memory_model_pso.cpp
@@ -16,7 +16,7 @@ void memory_model_psot::operator()(symex_target_equationt &equation)
   statistics() << "Adding PSO constraints" << eom;
 
   build_event_lists(equation);
-  build_clock_type(equation);
+  build_clock_type();
 
   read_from(equation);
   write_serialization_external(equation);
diff --git a/src/goto-symex/memory_model_sc.cpp b/src/goto-symex/memory_model_sc.cpp
index cfe30c80766..a09f9652f30 100644
--- a/src/goto-symex/memory_model_sc.cpp
+++ b/src/goto-symex/memory_model_sc.cpp
@@ -18,7 +18,7 @@ void memory_model_sct::operator()(symex_target_equationt &equation)
   statistics() << "Adding SC constraints" << eom;
 
   build_event_lists(equation);
-  build_clock_type(equation);
+  build_clock_type();
 
   read_from(equation);
   write_serialization_external(equation);
diff --git a/src/goto-symex/memory_model_tso.cpp b/src/goto-symex/memory_model_tso.cpp
index 5b390267086..8bf28a28813 100644
--- a/src/goto-symex/memory_model_tso.cpp
+++ b/src/goto-symex/memory_model_tso.cpp
@@ -19,7 +19,7 @@ void memory_model_tsot::operator()(symex_target_equationt &equation)
   statistics() << "Adding TSO constraints" << eom;
 
   build_event_lists(equation);
-  build_clock_type(equation);
+  build_clock_type();
 
   read_from(equation);
   write_serialization_external(equation);
diff --git a/src/goto-symex/partial_order_concurrency.cpp b/src/goto-symex/partial_order_concurrency.cpp
index bd05a170109..fb9529a83fb 100644
--- a/src/goto-symex/partial_order_concurrency.cpp
+++ b/src/goto-symex/partial_order_concurrency.cpp
@@ -161,8 +161,7 @@ symbol_exprt partial_order_concurrencyt::clock(
   return symbol_exprt(identifier, clock_type);
 }
 
-void partial_order_concurrencyt::build_clock_type(
-  const symex_target_equationt &equation)
+void partial_order_concurrencyt::build_clock_type()
 {
   assert(!numbering.empty());
 
diff --git a/src/goto-symex/partial_order_concurrency.h b/src/goto-symex/partial_order_concurrency.h
index adb82366cbd..759e240b98b 100644
--- a/src/goto-symex/partial_order_concurrency.h
+++ b/src/goto-symex/partial_order_concurrency.h
@@ -77,7 +77,7 @@ class partial_order_concurrencyt:public messaget
   // produce a clock symbol for some event
   typet clock_type;
   symbol_exprt clock(event_it e, axiomt axiom);
-  void build_clock_type(const symex_target_equationt &);
+  void build_clock_type();
 
   // preprocess and add a constraint to equation
   void add_constraint(