diff --git a/src/ast/rewriter/hoist_rewriter.cpp b/src/ast/rewriter/hoist_rewriter.cpp
index d3f5af2b573..d5b2042a2d0 100644
--- a/src/ast/rewriter/hoist_rewriter.cpp
+++ b/src/ast/rewriter/hoist_rewriter.cpp
@@ -23,7 +23,7 @@ Module Name:
 #include "ast/ast_ll_pp.h"
 
 hoist_rewriter::hoist_rewriter(ast_manager & m, params_ref const & p):
-    m(m), m_args1(m), m_args2(m), m_subst(m) { 
+    m(m), m_args1(m), m_args2(m), m_refs(m), m_subst(m) { 
     updt_params(p); 
 }
 
@@ -185,7 +185,7 @@ expr_ref hoist_rewriter::hoist_predicates(obj_hashtable<expr> const& preds, unsi
 
 br_status hoist_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * const * args, expr_ref & result) {
     switch (f->get_decl_kind()) {
-    case OP_OR:
+    case OP_OR:        
         return mk_or(num_args, args, result);
     default:
         return BR_FAILED;
@@ -193,6 +193,33 @@ br_status hoist_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * c
 }
 
 bool hoist_rewriter::is_and(expr * e, expr_ref_vector* args) {
+#if 0
+    if (!args) 
+        return m.is_and(e) || (m.is_not(e, e) && m.is_or(e));
+    expr_fast_mark1 visited;
+    args->reset();
+    args->push_back(e);
+    m_refs.reset();
+    for (unsigned i = 0; i < args->size(); ++i) {
+        e = args->get(i);
+        if (visited.is_marked(e)) 
+            goto drop;
+        m_refs.push_back(e);
+        visited.mark(e, true);
+        if (m.is_and(e)) 
+            args->append(to_app(e)->get_num_args(), to_app(e)->get_args());
+        else if (m.is_not(e, e) && m.is_or(e)) 
+            for (expr* arg : *to_app(e)) 
+                args->push_back(::mk_not(m, arg));
+        else 
+            continue;
+    drop:
+        (*args)[i] = args->back();
+        args->pop_back();
+        --i;
+    }
+    return args->size() > 1;
+#else
     if (m.is_and(e)) {
         if (args) {
             args->reset();
@@ -209,6 +236,7 @@ bool hoist_rewriter::is_and(expr * e, expr_ref_vector* args) {
         }
         return true;
     }
+#endif
     return false;
 }
 
diff --git a/src/ast/rewriter/hoist_rewriter.h b/src/ast/rewriter/hoist_rewriter.h
index ae7dff3bc51..b64325584a5 100644
--- a/src/ast/rewriter/hoist_rewriter.h
+++ b/src/ast/rewriter/hoist_rewriter.h
@@ -29,7 +29,7 @@ class bool_rewriter;
 
 class hoist_rewriter {
     ast_manager &                   m;
-    expr_ref_vector                 m_args1, m_args2;
+    expr_ref_vector                 m_args1, m_args2, m_refs;
     obj_hashtable<expr>             m_preds1, m_preds2;
     basic_union_find                m_uf1, m_uf2, m_uf0;
     ptr_vector<expr>                m_es;