diff --git a/src/codegen/codegen_helper_visitor.cpp b/src/codegen/codegen_helper_visitor.cpp
index 391dbc6d3..3ccee518d 100644
--- a/src/codegen/codegen_helper_visitor.cpp
+++ b/src/codegen/codegen_helper_visitor.cpp
@@ -252,7 +252,7 @@ void CodegenHelperVisitor::find_non_range_variables() {
 
     auto vars = psymtab->get_variables_with_properties(NmodlType::global_var);
     for (auto& var: vars) {
-        if (info.vectorize && info.thread_safe && var->get_write_count() > 0) {
+        if (info.vectorize && info.declared_thread_safe && var->get_write_count() > 0) {
             var->mark_thread_safe();
             info.thread_variables.push_back(var);
             info.thread_var_data_size += var->get_length();
@@ -767,6 +767,10 @@ void CodegenHelperVisitor::visit_bbcore_pointer(const BbcorePointer& /* node */)
     info.bbcore_pointer_used = true;
 }
 
+void CodegenHelperVisitor::visit_thread_safe(const ast::ThreadSafe&) {
+    info.declared_thread_safe = true;
+}
+
 
 void CodegenHelperVisitor::visit_watch(const ast::Watch& /* node */) {
     info.watch_count++;
diff --git a/src/codegen/codegen_helper_visitor.hpp b/src/codegen/codegen_helper_visitor.hpp
index 3468802c6..24d074f7a 100644
--- a/src/codegen/codegen_helper_visitor.hpp
+++ b/src/codegen/codegen_helper_visitor.hpp
@@ -101,6 +101,7 @@ class CodegenHelperVisitor: public visitor::ConstAstVisitor {
     void visit_derivimplicit_callback(const ast::DerivimplicitCallback& node) override;
     void visit_net_receive_block(const ast::NetReceiveBlock& node) override;
     void visit_bbcore_pointer(const ast::BbcorePointer& node) override;
+    void visit_thread_safe(const ast::ThreadSafe&) override;
     void visit_watch(const ast::Watch& node) override;
     void visit_watch_statement(const ast::WatchStatement& node) override;
     void visit_for_netcon(const ast::ForNetcon& node) override;
diff --git a/src/codegen/codegen_info.hpp b/src/codegen/codegen_info.hpp
index 0e86ac0c3..eaea56467 100644
--- a/src/codegen/codegen_info.hpp
+++ b/src/codegen/codegen_info.hpp
@@ -352,6 +352,12 @@ struct CodegenInfo {
     /// if mod file is thread safe (always true for coreneuron)
     bool thread_safe = true;
 
+    /// A mod file can be declared to be thread safe using the keyword THREADSAFE.
+    /// This boolean is true if and only if the mod file was declared thread safe
+    /// by the user. For example thread variables require the mod file to be declared
+    /// thread safe.
+    bool declared_thread_safe = false;
+
     /// if mod file is point process
     bool point_process = false;