diff --git a/src/cmd_context/cmd_context.h b/src/cmd_context/cmd_context.h
index f3fe5078e..9aac7bf06 100644
--- a/src/cmd_context/cmd_context.h
+++ b/src/cmd_context/cmd_context.h
@@ -125,7 +125,7 @@ public:
     virtual bool is_pareto() = 0;
     virtual void set_logic(symbol const& s) = 0;
     virtual bool print_model() const = 0;
-    virtual void updt_params(params_ref& p) = 0;
+    virtual void updt_params(params_ref const& p) = 0;
 };
 
 class cmd_context : public progress_callback, public tactic_manager, public ast_printer_context {
diff --git a/src/opt/opt_context.cpp b/src/opt/opt_context.cpp
index 369c6e2b1..d20b2e5f6 100644
--- a/src/opt/opt_context.cpp
+++ b/src/opt/opt_context.cpp
@@ -1298,7 +1298,7 @@ namespace opt {
         opt_params::collect_param_descrs(r);
     }
     
-    void context::updt_params(params_ref& p) {
+    void context::updt_params(params_ref const& p) {
         m_params.append(p);
         if (m_solver) {
             m_solver->updt_params(m_params);
diff --git a/src/opt/opt_context.h b/src/opt/opt_context.h
index ff3be1cd2..f581c7df2 100644
--- a/src/opt/opt_context.h
+++ b/src/opt/opt_context.h
@@ -195,7 +195,7 @@ namespace opt {
 
         void display(std::ostream& out);
         static void collect_param_descrs(param_descrs & r);
-        virtual void updt_params(params_ref& p);
+        virtual void updt_params(params_ref const& p);
         params_ref& get_params() { return m_params; }
 
         expr_ref get_lower(unsigned idx);