diff --git a/src/ast/finite_set_decl_plugin.cpp b/src/ast/finite_set_decl_plugin.cpp
index ce8bba262..891d5f6b9 100644
--- a/src/ast/finite_set_decl_plugin.cpp
+++ b/src/ast/finite_set_decl_plugin.cpp
@@ -183,7 +183,9 @@ expr * finite_set_decl_plugin::get_some_value(sort * s) {
 }
 
 bool finite_set_decl_plugin::is_fully_interp(sort * s) const {
-    return false;
+    SASSERT(is_finite_set(s));
+    sort* element_sort = get_element_sort(s);
+    return element_sort && m_manager->is_fully_interp(element_sort);
 }
 
 bool finite_set_decl_plugin::is_value(app * e) const {
diff --git a/src/ast/rewriter/finite_set_rewriter.h b/src/ast/rewriter/finite_set_rewriter.h
index 95651c815..1dc536946 100644
--- a/src/ast/rewriter/finite_set_rewriter.h
+++ b/src/ast/rewriter/finite_set_rewriter.h
@@ -33,7 +33,17 @@ where the signature is defined in finite_set_decl_plugin.h.
    \brief Cheap rewrite rules for finite sets
 */
 class finite_set_rewriter {
+    friend class finite_set_rewriter_test;
     finite_set_util  m_util;
+
+    // Rewrite rules for set operations
+    br_status mk_union(unsigned num_args, expr *const *args, expr_ref &result);
+    br_status mk_intersect(unsigned num_args, expr *const *args, expr_ref &result);
+    br_status mk_difference(expr *arg1, expr *arg2, expr_ref &result);
+    br_status mk_subset(expr *arg1, expr *arg2, expr_ref &result);
+    br_status mk_singleton(expr *arg1, expr_ref &result);
+    br_status mk_in(expr *arg1, expr *arg2, expr_ref &result);
+
 public:
     finite_set_rewriter(ast_manager & m, params_ref const & p = params_ref()):
         m_util(m) {
@@ -43,15 +53,6 @@ public:
     family_id get_fid() const { return m_util.get_family_id(); }
     finite_set_util& util() { return m_util; }
 
-    br_status mk_app_core(func_decl * f, unsigned num_args, expr * const * args, expr_ref & result);
-    
-    // Rewrite rules for set operations
-    br_status mk_union(unsigned num_args, expr * const * args, expr_ref & result);
-    br_status mk_intersect(unsigned num_args, expr * const * args, expr_ref & result);
-    br_status mk_difference(expr * arg1, expr * arg2, expr_ref & result);
-    br_status mk_subset(expr * arg1, expr * arg2, expr_ref & result);
-    br_status mk_singleton(expr *arg1, expr_ref &result);
-    br_status mk_in(expr *arg1, expr *arg2, expr_ref &result);
-
+    br_status mk_app_core(func_decl * f, unsigned num_args, expr * const * args, expr_ref & result);   
 };
 
diff --git a/src/test/finite_set.cpp b/src/test/finite_set.cpp
index d6ab4775d..d9b9ee515 100644
--- a/src/test/finite_set.cpp
+++ b/src/test/finite_set.cpp
@@ -131,16 +131,21 @@ static void tst_finite_set_is_value() {
     ast_manager m;
     reg_decl_plugins(m);
     
+
+    
     finite_set_util fsets(m);
     arith_util arith(m);
     finite_set_decl_plugin* plugin = static_cast<finite_set_decl_plugin*>(m.get_plugin(fsets.get_family_id()));
+  
+      // Create Int sort and finite set sort
     
-    // Create Int sort and finite set sort
+    // Test with Int sort (should be fully interpreted)
     sort_ref int_sort(arith.mk_int(), m);
     parameter int_param(int_sort.get());
     sort_ref finite_set_int(m.mk_sort(fsets.get_family_id(), FINITE_SET_SORT, 1, &int_param), m);
     
-    // Test 1: Empty set is a value
+    
+  // Test 1: Empty set is a value
     app_ref empty_set(fsets.mk_empty(finite_set_int), m);
     ENSURE(plugin->is_value(empty_set.get()));
     
@@ -187,10 +192,34 @@ static void tst_finite_set_is_value() {
     // Test 10: Intersect is NOT a value
     app_ref intersect_set(fsets.mk_intersect(singleton_five, singleton_seven), m);
     ENSURE(!plugin->is_value(intersect_set.get()));
+    ENSURE(m.is_fully_interp(int_sort));
+    ENSURE(m.is_fully_interp(finite_set_int));
+}
+
+static void tst_finite_set_is_fully_interp() {
+    ast_manager m;
+    reg_decl_plugins(m);
+    
+    // Test with Bool sort (should be fully interpreted)
+    sort_ref bool_sort(m.mk_bool_sort(), m);
+    parameter bool_param(bool_sort.get());
+    sort_ref finite_set_bool(m.mk_sort(fsets.get_family_id(), FINITE_SET_SORT, 1, &bool_param), m);
+    
+    ENSURE(m.is_fully_interp(bool_sort));
+    ENSURE(m.is_fully_interp(finite_set_bool));
+    
+    // Test with uninterpreted sort (should not be fully interpreted)
+    sort_ref uninterp_sort(m.mk_uninterpreted_sort(symbol("U")), m);
+    parameter uninterp_param(uninterp_sort.get());
+    sort_ref finite_set_uninterp(m.mk_sort(fsets.get_family_id(), FINITE_SET_SORT, 1, &uninterp_param), m);
+    
+    ENSURE(!m.is_fully_interp(uninterp_sort));
+    ENSURE(!m.is_fully_interp(finite_set_uninterp));
 }
 
 void tst_finite_set() {
     tst_finite_set_basic();
     tst_finite_set_map_select();
     tst_finite_set_is_value();
+    tst_finite_set_is_fully_interp();
 }