diff --git a/boot/symbol.cc b/boot/symbol.cc
index ffa56a7..fef6ab6 100644
--- a/boot/symbol.cc
+++ b/boot/symbol.cc
@@ -339,7 +339,7 @@ namespace elna::boot
 
     std::shared_ptr<variable_info> variable_info::is_variable()
     {
-        return std::static_pointer_cast<variable_info>(shared_from_this());;
+        return std::static_pointer_cast<variable_info>(shared_from_this());
     }
 
     std::shared_ptr<symbol_table> builtin_symbol_table()
diff --git a/gcc/elna-generic.cc b/gcc/elna-generic.cc
index 7774e1c..99250df 100644
--- a/gcc/elna-generic.cc
+++ b/gcc/elna-generic.cc
@@ -148,7 +148,7 @@ namespace elna::gcc
             if (!is_assignable_from(TREE_VALUE(current_parameter), this->current_expression))
             {
                 error_at(argument_location,
-                        "cannot assign value of type '%s' to variable of type '%s'",
+                        "Cannot assign value of type '%s' to variable of type '%s'",
                         print_type(TREE_TYPE(this->current_expression)).c_str(),
                         print_type(TREE_VALUE(current_parameter)).c_str());
                 this->current_expression = error_mark_node;
@@ -215,6 +215,49 @@ namespace elna::gcc
     void generic_visitor::visit(boot::procedure_call *call)
     {
         location_t call_location = get_location(&call->position());
+
+        if (boot::variable_expression *named_call = call->callable().is_variable())
+        {
+            if (named_call->name == "assert")
+            {
+                if (call->arguments.size() != 1)
+                {
+                    error_at(call_location, "assert expects exactly one boolean argument, got %lu",
+                            call->arguments.size());
+                    this->current_expression = error_mark_node;
+                }
+                else
+                {
+                    call->arguments.at(0)->accept(this);
+                    tree argument_type = TREE_TYPE(this->current_expression);
+
+                    if (argument_type != elna_bool_type_node)
+                    {
+                        error_at(call_location, "assert expects exactly one boolean argument, got %s",
+                                print_type(argument_type).c_str());
+                        this->current_expression = error_mark_node;
+                    }
+                    tree constant_expression = extract_constant(this->current_expression);
+                    if (constant_expression == boolean_false_node)
+                    {
+                        tree *builtin = elna_global_decls->get("__builtin_unreachable");
+                        gcc_assert(builtin != nullptr);
+
+                        tree fndecl_type = build_function_type(void_type_node, TYPE_ARG_TYPES(*builtin));
+                        tree builtin_addr = build1_loc(call_location, ADDR_EXPR,
+                                build_pointer_type(fndecl_type), *builtin);
+
+                        this->current_expression = build_call_nary(void_type_node, builtin_addr, 1,
+                                this->current_expression);
+                    }
+                    else
+                    {
+                        this->current_expression = NULL_TREE;
+                    }
+                }
+                return;
+            }
+        }
         call->callable().accept(this);
 
         tree expression_type = TYPE_P(this->current_expression)
@@ -768,7 +811,7 @@ namespace elna::gcc
         location_t definition_location = get_location(&definition->position());
         definition->body().accept(this);
 
-        if (extract_constant(definition_location))
+        if (assert_constant(definition_location))
         {
             this->current_expression = fold_init(this->current_expression);
         }
@@ -1490,7 +1533,7 @@ namespace elna::gcc
                 case_label->accept(this);
                 location_t case_location = get_location(&case_label->position());
 
-                if (extract_constant(case_location)
+                if (assert_constant(case_location)
                         && !is_assignable_from(unqualified_condition, this->current_expression))
                 {
                     error_at(case_location, "Case type '%s' does not match the expression type '%s'",
@@ -1535,20 +1578,19 @@ namespace elna::gcc
         this->current_expression = NULL_TREE;
     }
 
-    bool generic_visitor::extract_constant(location_t expression_location)
+    bool generic_visitor::assert_constant(location_t expression_location)
     {
-        int code = TREE_CODE(this->current_expression);
+        tree constant_expression = extract_constant(this->current_expression);
 
-        if (code == CONST_DECL)
-        {
-            this->current_expression = DECL_INITIAL(this->current_expression);
-        }
-        else if (TREE_CODE_CLASS(code) != tcc_constant)
+        if (constant_expression == NULL_TREE)
         {
             error_at(expression_location, "Expected a constant expression");
             this->current_expression = error_mark_node;
-            return false;
         }
-        return true;
+        else
+        {
+            this->current_expression = constant_expression;
+        }
+        return this->current_expression != error_mark_node;
     }
 }
diff --git a/gcc/elna-tree.cc b/gcc/elna-tree.cc
index a1d7f0b..3767ea9 100644
--- a/gcc/elna-tree.cc
+++ b/gcc/elna-tree.cc
@@ -249,4 +249,19 @@ namespace elna::gcc
 
         return label_decl;
     }
+
+    tree extract_constant(tree expression)
+    {
+        int code = TREE_CODE(expression);
+
+        if (code == CONST_DECL)
+        {
+            return DECL_INITIAL(expression);
+        }
+        else if (TREE_CODE_CLASS(code) == tcc_constant)
+        {
+            return expression;
+        }
+        return NULL_TREE;
+    }
 }
diff --git a/include/elna/gcc/elna-generic.h b/include/elna/gcc/elna-generic.h
index 968238b..5db21ea 100644
--- a/include/elna/gcc/elna-generic.h
+++ b/include/elna/gcc/elna-generic.h
@@ -72,7 +72,7 @@ namespace elna::gcc
         bool expect_trait_type_only(boot::traits_expression *trait);
         bool expect_trait_for_integral_type(boot::traits_expression *trait);
         void visit_statements(const std::vector<boot::statement *>& statements);
-        bool extract_constant(location_t expression_location);
+        bool assert_constant(location_t expression_location);
 
     public:
         generic_visitor(std::shared_ptr<symbol_table> symbol_table,
diff --git a/include/elna/gcc/elna-tree.h b/include/elna/gcc/elna-tree.h
index 335dc0c..0f660d2 100644
--- a/include/elna/gcc/elna-tree.h
+++ b/include/elna/gcc/elna-tree.h
@@ -82,4 +82,6 @@ namespace elna::gcc
     tree find_field_by_name(location_t expression_location, tree type, const std::string& field_name);
     tree build_global_pointer_type(tree type);
     tree build_label_decl(const char *name, location_t loc);
+
+    tree extract_constant(tree expression);
 }