diff --git a/include/ast/scope.hpp b/include/ast/scope.hpp
index aa3a57b..daaca55 100644
--- a/include/ast/scope.hpp
+++ b/include/ast/scope.hpp
@@ -30,7 +30,7 @@ class LocalScope : public ScopeBase {
   std::unordered_map<std::string, ExprTypeInfo> local_variables;
   bool add_variable(const std::string &name, const ExprTypeInfo &type) override {
     if (!VariableNameAvailable(name, 0)) {
-      throw std::runtime_error("Variable name " + name + " is not available");
+      return false;
     }
     local_variables[name] = type;
     return true;
@@ -78,7 +78,7 @@ class ClassDefScope : public ScopeBase {
   std::unordered_map<std::string, std::shared_ptr<FunctionScope>> member_functions;
   bool add_variable(const std::string &name, const ExprTypeInfo &type) override {
     if (!VariableNameAvailable(name, 0)) {
-      throw std::runtime_error("Variable name " + name + " is not available");
+      return false;
     }
     member_variables[name] = type;
     return true;
@@ -98,6 +98,11 @@ class ClassDefScope : public ScopeBase {
     if (ttl == 0 && IsKeyWord(name)) {
       return false;
     }
+    if (ttl == 0) {
+      if (member_variables.find(name) != member_variables.end()) {
+        return false;
+      }
+    }
     if (member_functions.find(name) != member_functions.end()) {
       return false;
     }
@@ -139,7 +144,7 @@ class GlobalScope : public ScopeBase {
   }
   bool add_variable(const std::string &name, const ExprTypeInfo &type) override {
     if (!VariableNameAvailable(name, 0)) {
-      throw std::runtime_error("Variable name " + name + " is not available");
+      return false;
     }
     global_variables[name] = type;
     return true;
@@ -148,13 +153,15 @@ class GlobalScope : public ScopeBase {
     if (ttl == 0 && IsKeyWord(name)) {
       return false;
     }
-    if (global_variables.find(name) != global_variables.end()) {
-      return false;
+    if (ttl == 0) {
+      if (global_variables.find(name) != global_variables.end()) {
+        return false;
+      }
     }
-    if (classes.find(name) != classes.end()) {
-      return false;
-    }
-    if (classes.find(name) != classes.end()) {
+    // if (classes.find(name) != classes.end()) {
+    //   return false;
+    // }
+    if (global_functions.find(name) != global_functions.end()) {
       return false;
     }
     return true;
diff --git a/src/semantic/visitor.cpp b/src/semantic/visitor.cpp
index 90835d2..31802f2 100644
--- a/src/semantic/visitor.cpp
+++ b/src/semantic/visitor.cpp
@@ -453,6 +453,12 @@ std::any Visitor::visitDefine_statement(MXParser::Define_statementContext *conte
   def_stmt->end_char_pos = context->getStop()->getCharPositionInLine();
   assert(nodetype_stk.size() > 0);
   def_stmt->current_scope = nodetype_stk.back().second;
+  if (nodetype_stk.size() > 0 && (nodetype_stk.back().first == ASTNodeType::IfStatement ||
+                                  nodetype_stk.back().first == ASTNodeType::WhileStatement ||
+                                  nodetype_stk.back().first == ASTNodeType::ForStatement)) {
+    def_stmt->current_scope = std::make_shared<LocalScope>();
+    def_stmt->current_scope->parent = nodetype_stk.back().second.get();
+  }
   nodetype_stk.push_back({ASTNodeType::DefinitionStatement, def_stmt->current_scope});
   std::cerr << std::string(nodetype_stk.size() * 2, ' ') << "Adding a definition statement" << std::endl;
   std::string define_type_base;