diff --git a/src/ast/ast.cpp b/src/ast/ast.cpp
index 2881f1b62..f17e40873 100644
--- a/src/ast/ast.cpp
+++ b/src/ast/ast.cpp
@@ -1023,8 +1023,11 @@ sort* basic_decl_plugin::join(sort* s1, sort* s2) {
         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,
diff --git a/src/cmd_context/context_params.cpp b/src/cmd_context/context_params.cpp
index 8760ade15..5a9b1a4f3 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();
 }
@@ -130,7 +130,7 @@ void context_params::updt_params(params_ref const & p) {
 
 void context_params::collect_param_descrs(param_descrs & d) {
     d.insert("timeout", CPK_UINT, "default timeout (in milliseconds) used for solvers", "4294967295");
-    d.insert("well_sorted_check", CPK_BOOL, "type checker", "true");
+    d.insert("well_sorted_check", CPK_BOOL, "type checker", "false");
     d.insert("type_check", CPK_BOOL, "type checker (alias for well_sorted_check)", "true");
     d.insert("auto_config", CPK_BOOL, "use heuristics to automatically select solver and configure it", "true");
     d.insert("model_validate", CPK_BOOL, "validate models produced by solvers", "false");