diff --git a/code/compiler/13/ast.cpp b/code/compiler/13/ast.cpp
index 24e769a..efa84a4 100644
--- a/code/compiler/13/ast.cpp
+++ b/code/compiler/13/ast.cpp
@@ -340,7 +340,7 @@ struct case_strategy_data {
             std::vector<instruction_ptr>& into) {
         env_ptr new_env = env;
         for(auto it = repr.second->rbegin(); it != repr.second->rend(); it++) {
-            new_env = env_ptr(new env_var(branch->expr->env->get_mangled_name(*it), new_env));
+            new_env = env_ptr(new env_var(*it, new_env));
         }
 
         into.push_back(instruction_ptr(new instruction_split(repr.second->size())));
@@ -392,7 +392,7 @@ void compile_case(const ast_case& node, const env_ptr& env, const type* type, st
             if(cases.defined_cases_count() == strategy.case_count(type))
                 throw type_error("redundant catch-all pattern", branch->pat->loc);
             auto& branch_into = cases.make_default_case();
-            env_ptr new_env(new env_var(branch->expr->env->get_mangled_name(vpat->var), env));
+            env_ptr new_env(new env_var(vpat->var, env));
             branch->expr->compile(new_env, branch_into);
             branch_into.push_back(instruction_ptr(new instruction_slide(1)));
         } else {
@@ -484,7 +484,7 @@ void ast_let::compile(const env_ptr& env, std::vector<instruction_ptr>& into) co
     into.push_back(instruction_ptr(new instruction_alloc(translated_definitions.size())));
     env_ptr new_env = env;
     for(auto& def : translated_definitions) {
-        new_env = env_ptr(new env_var(definitions.env->get_mangled_name(def.first), std::move(new_env)));
+        new_env = env_ptr(new env_var(def.first, std::move(new_env)));
     }
     int offset = translated_definitions.size() - 1;
     for(auto& def : translated_definitions) {
diff --git a/code/compiler/13/type_env.cpp b/code/compiler/13/type_env.cpp
index 4c5d3ad..5070f8c 100644
--- a/code/compiler/13/type_env.cpp
+++ b/code/compiler/13/type_env.cpp
@@ -34,7 +34,12 @@ bool type_env::is_global(const std::string& name) const {
 
 void type_env::set_mangled_name(const std::string& name, const std::string& mangled) {
     auto it = names.find(name);
-    if(it != names.end()) it->second.mangled_name = mangled;
+    if(it != names.end()) {
+        // Local names shouldn't need mangling.
+        assert(it->second.vis == visibility::global);
+
+        it->second.mangled_name = mangled;
+    }
 }
 
 const std::string& type_env::get_mangled_name(const std::string& name) const {