diff --git a/src/thorin/be/c/c.cpp b/src/thorin/be/c/c.cpp
index 398e6dac4..346f88995 100644
--- a/src/thorin/be/c/c.cpp
+++ b/src/thorin/be/c/c.cpp
@@ -369,6 +369,17 @@ std::string CCodeGen::convert(const Type* type) {
             s.rangei(struct_type->ops(), "\n", [&] (size_t i) { s.fmt("{} {};", convert(struct_type->types()[i]), struct_type->op_name(i)); });
             s.fmt("\b\n}} {};\n", name);
         }
+    } else if (auto extern_type = type->isa<ExternType>()) {
+        if (extern_type->name() == "c.typedef") {
+            types_[extern_type] = name = extern_type->unique_name();
+            assert(extern_type->num_ops() == 1 && "External type in C backend unsupported.");
+            auto first_arg = extern_type->op(0);
+            assert(first_arg->isa<DefiniteArray>() && "Only strings as argument.");
+            s.fmt("typedef {} {};\n", first_arg->as<DefiniteArray>()->as_string(), name);
+        } else {
+            world().edef(extern_type, "unsupported extern_type");
+            s.fmt("/* unsupported */");
+        }
     } else {
         THORIN_UNREACHABLE;
     }
diff --git a/src/thorin/rec_stream.cpp b/src/thorin/rec_stream.cpp
index 590693e31..9a657efc2 100644
--- a/src/thorin/rec_stream.cpp
+++ b/src/thorin/rec_stream.cpp
@@ -234,6 +234,9 @@ Stream& Type::stream(Stream& s) const {
 
         if (t->is_vector()) s.fmt(">");
         return s;
+    } else if (auto t = isa<ExternType>()) {
+        s.fmt("{}", t->name());
+        return s;
     }
     THORIN_UNREACHABLE;
 }
diff --git a/src/thorin/tables/nodetable.h b/src/thorin/tables/nodetable.h
index 8c17d04dc..79938cc94 100644
--- a/src/thorin/tables/nodetable.h
+++ b/src/thorin/tables/nodetable.h
@@ -57,6 +57,7 @@
         THORIN_NODE(Lambda, lambda)
         THORIN_NODE(MemType, mem)
         THORIN_NODE(BotType, bot_ty)
+        THORIN_NODE(ExternType, ext_ty)
         THORIN_NODE(PtrType, ptr)
         THORIN_NODE(StructType, struct_type)
         THORIN_NODE(VariantType, variant_type)
diff --git a/src/thorin/transform/closure_conversion.cpp b/src/thorin/transform/closure_conversion.cpp
index 2048d77a5..0b937578b 100644
--- a/src/thorin/transform/closure_conversion.cpp
+++ b/src/thorin/transform/closure_conversion.cpp
@@ -205,6 +205,14 @@ class ClosureConversion {
             // struct types cannot be rebuilt and need to be put in the map first to avoid infinite recursion
             new_type = world_.struct_type(type->as<StructType>()->name(), ops.size());
             new_types_[type] = new_type;
+        } else if (type->isa<VariantType>()) {
+            // struct types cannot be rebuilt and need to be put in the map first to avoid infinite recursion
+            new_type = world_.variant_type(type->as<VariantType>()->name(), ops.size());
+            new_types_[type] = new_type;
+        } else if (type->isa<ExternType>()) {
+            // struct types cannot be rebuilt and need to be put in the map first to avoid infinite recursion
+            new_type = world_.extern_type(type->as<ExternType>()->name(), ops.size());
+            new_types_[type] = new_type;
         }
 
         // accept one parameter of order 1 (the return continuation) for function types
@@ -223,6 +231,14 @@ class ClosureConversion {
             StructType* struct_type = const_cast<StructType*>(new_type->as<StructType>());
             for (size_t i = 0, e = ops.size(); i != e; ++i)
                 struct_type->set_op(i, ops[i]);
+        } else if (type->isa<VariantType>()) {
+            VariantType* variant_type = const_cast<VariantType*>(new_type->as<VariantType>());
+            for (size_t i = 0, e = ops.size(); i != e; ++i)
+                variant_type->set_op(i, ops[i]);
+        } else if (type->isa<ExternType>()) {
+            ExternType* extern_type = const_cast<ExternType*>(new_type->as<ExternType>());
+            for (size_t i = 0, e = ops.size(); i != e; ++i)
+                extern_type->set_op(i, ops[i]);
         } else {
             new_type = type->rebuild(world_, type->type(), ops)->as<Type>();
         }
diff --git a/src/thorin/type.cpp b/src/thorin/type.cpp
index 837d6ff2d..e5317a7e1 100644
--- a/src/thorin/type.cpp
+++ b/src/thorin/type.cpp
@@ -78,6 +78,10 @@ VariantType* VariantType::stub(Rewriter& rewriter, const Type*) const {
     return type;
 }
 
+ExternType* ExternType::stub(Rewriter& rewriter, const Type*) const {
+    return rewriter.dst().extern_type(name(), num_ops(), debug());
+}
+
 //------------------------------------------------------------------------------
 
 const VectorType* VectorType::scalarize() const {
@@ -157,6 +161,10 @@ VariantType* World::variant_type(Symbol name, size_t size) {
     return put<VariantType>(*this, name, size, Debug());
 }
 
+ExternType* World::extern_type(Symbol name, size_t size, Debug dbg) {
+    return put<ExternType>(*this, name, size, dbg);
+}
+
 const PrimType* World::prim_type(PrimTypeTag tag, size_t length) {
     size_t i = tag - Begin_PrimType;
     assert(i < (size_t) Num_PrimTypes);
diff --git a/src/thorin/type.h b/src/thorin/type.h
index 8d69b4aa2..f479ba344 100644
--- a/src/thorin/type.h
+++ b/src/thorin/type.h
@@ -133,6 +133,17 @@ class VariantType : public NominalType, public TypeOpsMixin<VariantType> {
     friend class World;
 };
 
+class ExternType : public NominalType {
+private:
+    ExternType(World& world, Symbol name, size_t size, Debug dbg)
+        : NominalType(world, Node_ExternType, name, size, dbg) {}
+
+public:
+    virtual ExternType* stub(Rewriter&, const Type*) const override;
+
+    friend class World;
+};
+
 /// The type of the memory monad.
 class MemType : public Type {
 private:
diff --git a/src/thorin/world.h b/src/thorin/world.h
index 4b77d8072..4777d2ca9 100644
--- a/src/thorin/world.h
+++ b/src/thorin/world.h
@@ -110,6 +110,7 @@ class World : public Streamable<World> {
     const TupleType* unit_type() { return tuple_type({})->as<TupleType>(); } ///< Returns unit, i.e., an empty @p TupleType.
     VariantType* variant_type(Symbol name, size_t size);
     StructType* struct_type(Symbol name, size_t size);
+    ExternType* extern_type(Symbol name, size_t size, Debug = {});
 
 #define THORIN_ALL_TYPE(T, M) \
     const PrimType* type_##T(size_t length = 1) { return prim_type(PrimType_##T, length); }