diff --git a/src/ast/seq_decl_plugin.cpp b/src/ast/seq_decl_plugin.cpp
index 111b567da..ea073f23f 100644
--- a/src/ast/seq_decl_plugin.cpp
+++ b/src/ast/seq_decl_plugin.cpp
@@ -417,7 +417,7 @@ func_decl * seq_decl_plugin::mk_func_decl(decl_kind k, unsigned num_parameters,
         match(*m_sigs[k], arity, domain, range, rng);
         return m.mk_func_decl(m_sigs[k]->m_name, arity, domain, rng, func_decl_info(m_family_id, k));
     case OP_STRING_UBVTOS:
-        NOT_IMPLEMENTED_YET();
+        return mk_ubv2s(arity, domain);        
 
     case _OP_REGEXP_FULL_CHAR:
         m_has_re = true;