diff --git a/src/ast/ast.cpp b/src/ast/ast.cpp
index 2881f1b62..6e2fac4bd 100644
--- a/src/ast/ast.cpp
+++ b/src/ast/ast.cpp
@@ -1018,15 +1018,19 @@ func_decl * basic_decl_plugin::mk_ite_decl(sort * s) {
 
 sort* basic_decl_plugin::join(sort* s1, sort* s2) {
     if (s1 == s2) return s1;
-    if (s1->get_family_id() == m_manager->m_arith_family_id && 
+    if (s1->get_family_id() == m_manager->m_arith_family_id &&
         s2->get_family_id() == m_manager->m_arith_family_id) {
         if (s1->get_decl_kind() == REAL_SORT) {
             return s1;
         }
+        return s2;
     }
-    return s2;
+    std::ostringstream buffer;
+    buffer << "Sorts " << mk_pp(s1, *m_manager) << " and " << mk_pp(s2, *m_manager) << " are incompatible";
+    throw ast_exception(buffer.str().c_str());
 }
 
+
 func_decl * basic_decl_plugin::mk_func_decl(decl_kind k, unsigned num_parameters, parameter const * parameters,
                                           unsigned arity, sort * const * domain, sort * range) {
     switch (static_cast<basic_op_kind>(k)) {
diff --git a/src/cmd_context/context_params.cpp b/src/cmd_context/context_params.cpp
index 8760ade15..70f110c92 100644
--- a/src/cmd_context/context_params.cpp
+++ b/src/cmd_context/context_params.cpp
@@ -33,7 +33,7 @@ context_params::context_params() {
     m_trace          = false;
     m_debug_ref_count = false;
     m_smtlib2_compliant = false;
-    m_well_sorted_check = true;
+    m_well_sorted_check = false;
     m_timeout = UINT_MAX;
     updt_params();
 }