diff --git a/src/ast/rewriter/th_rewriter.cpp b/src/ast/rewriter/th_rewriter.cpp
index 5b0df8147..c69534b08 100644
--- a/src/ast/rewriter/th_rewriter.cpp
+++ b/src/ast/rewriter/th_rewriter.cpp
@@ -78,7 +78,7 @@ struct th_rewriter_cfg : public default_rewriter_cfg {
 
     void updt_local_params(params_ref const & _p) {
         rewriter_params p(_p);
-        m_flat           = p.flat();
+        m_flat           = true;
         m_max_memory     = megabytes_to_bytes(p.max_memory());
         m_max_steps      = p.max_steps();
         m_pull_cheap_ite = p.pull_cheap_ite();
diff --git a/src/params/rewriter_params.pyg b/src/params/rewriter_params.pyg
index 18bb29e56..290f7b1da 100644
--- a/src/params/rewriter_params.pyg
+++ b/src/params/rewriter_params.pyg
@@ -3,7 +3,6 @@ def_module_params('rewriter',
                   export=True,
                   params=(max_memory_param(),
                           max_steps_param(),
-                          ("flat", BOOL, True, "create nary applications for and,or,+,*,bvadd,bvmul,bvand,bvor,bvxor"),
                           ("push_ite_arith", BOOL, False, "push if-then-else over arithmetic terms."),
                           ("push_ite_bv", BOOL, False, "push if-then-else over bit-vector terms."),
                           ("pull_cheap_ite", BOOL, False, "pull if-then-else terms when cheap."),