diff --git a/betterproto/compile/importing.py b/betterproto/compile/importing.py
index cdef91f..091812b 100644
--- a/betterproto/compile/importing.py
+++ b/betterproto/compile/importing.py
@@ -129,7 +129,8 @@ def import_ancestor(current_package, imports, py_package, py_type):
     distance_up = len(current_package) - len(py_package)
     if py_package:
         string_import = py_package[-1]
-        string_alias = f"__{'_' * distance_up}{string_import}"
+        # Add trailing __ to avoid name mangling (python.org/dev/peps/pep-0008/#id34)
+        string_alias = f"_{'_' * distance_up}{string_import}__"
         string_from = f"..{'.' * distance_up}"
         imports.add(f"from {string_from} import {string_import} as {string_alias}")
         return f"{string_alias}.{py_type}"
@@ -152,8 +153,9 @@ def import_cousin(current_package, imports, py_package, py_type):
         py_package[len(shared_ancestry) : -1]
     )
     string_import = py_package[-1]
-    alias = f"{'_' * distance_up}" + safe_snake_case(
+    # Add trailing __ to avoid name mangling (python.org/dev/peps/pep-0008/#id34)
+    string_alias = f"{'_' * distance_up}" + safe_snake_case(
         ".".join(py_package[len(shared_ancestry) :])
-    )
-    imports.add(f"from {string_from} import {string_import} as {alias}")
-    return f"{alias}.{py_type}"
+    ) + "__"
+    imports.add(f"from {string_from} import {string_import} as {string_alias}")
+    return f"{string_alias}.{py_type}"
diff --git a/betterproto/tests/inputs/casing_message_field_uppercase/casing_message_field_uppercase.py b/betterproto/tests/inputs/casing_message_field_uppercase/casing_message_field_uppercase.py
index d77119e..e0dee0c 100644
--- a/betterproto/tests/inputs/casing_message_field_uppercase/casing_message_field_uppercase.py
+++ b/betterproto/tests/inputs/casing_message_field_uppercase/casing_message_field_uppercase.py
@@ -1,6 +1,4 @@
-from betterproto.tests.output_betterproto.casing_message_field_uppercase.casing_message_field_uppercase import (
-    Test,
-)
+from betterproto.tests.output_betterproto.casing_message_field_uppercase import Test
 
 
 def test_message_casing():
diff --git a/betterproto/tests/inputs/nested/nested.proto b/betterproto/tests/inputs/nested/nested.proto
index 2eaef59..98bafd9 100644
--- a/betterproto/tests/inputs/nested/nested.proto
+++ b/betterproto/tests/inputs/nested/nested.proto
@@ -10,9 +10,9 @@ message Test {
 
     Nested nested = 1;
     Sibling sibling = 2;
-//    Sibling sibling2 = 3;
+    Sibling sibling2 = 3;
 }
 
 message Sibling {
   int32 foo = 1;
-}
+}
\ No newline at end of file
diff --git a/betterproto/tests/inputs/nested2/nested2.proto b/betterproto/tests/inputs/nested2/nested2.proto
new file mode 100644
index 0000000..3e39918
--- /dev/null
+++ b/betterproto/tests/inputs/nested2/nested2.proto
@@ -0,0 +1,19 @@
+syntax = "proto3";
+
+import "package.proto";
+
+message Game {
+    message Player {
+        enum Race {
+            human = 0;
+            orc = 1;
+        }
+    }
+}
+
+message Test {
+    Game game = 1;
+    Game.Player GamePlayer = 2;
+    Game.Player.Race GamePlayerRace = 3;
+    equipment.Weapon Weapon = 4;
+}
\ No newline at end of file
diff --git a/betterproto/tests/inputs/nested2/package.proto b/betterproto/tests/inputs/nested2/package.proto
new file mode 100644
index 0000000..4466256
--- /dev/null
+++ b/betterproto/tests/inputs/nested2/package.proto
@@ -0,0 +1,7 @@
+syntax = "proto3";
+
+package equipment;
+
+message Weapon {
+
+}
\ No newline at end of file
diff --git a/betterproto/tests/test_get_ref_type.py b/betterproto/tests/test_get_ref_type.py
index a2d089d..412b4ed 100644
--- a/betterproto/tests/test_get_ref_type.py
+++ b/betterproto/tests/test_get_ref_type.py
@@ -174,8 +174,8 @@ def test_import_parent_package_from_child():
         package="package.child", imports=imports, source_type="package.Message"
     )
 
-    assert imports == {"from ... import package as ___package"}
-    assert name == "___package.Message"
+    assert imports == {"from ... import package as __package__"}
+    assert name == "__package__.Message"
 
 
 def test_import_parent_package_from_deeply_nested_child():
@@ -186,8 +186,8 @@ def test_import_parent_package_from_deeply_nested_child():
         source_type="package.deeply.nested.Message",
     )
 
-    assert imports == {"from ... import nested as ___nested"}
-    assert name == "___nested.Message"
+    assert imports == {"from ... import nested as __nested__"}
+    assert name == "__nested__.Message"
 
 
 def test_import_ancestor_package_from_nested_child():
@@ -198,8 +198,8 @@ def test_import_ancestor_package_from_nested_child():
         source_type="package.ancestor.Message",
     )
 
-    assert imports == {"from .... import ancestor as ____ancestor"}
-    assert name == "____ancestor.Message"
+    assert imports == {"from .... import ancestor as ___ancestor__"}
+    assert name == "___ancestor__.Message"
 
 
 def test_import_root_package_from_child():
@@ -224,16 +224,16 @@ def test_import_unrelated_package():
     imports = set()
     name = get_ref_type(package="a", imports=imports, source_type="p.Message")
 
-    assert imports == {"from .. import p as _p"}
-    assert name == "_p.Message"
+    assert imports == {"from .. import p as _p__"}
+    assert name == "_p__.Message"
 
 
 def test_import_unrelated_nested_package():
     imports = set()
     name = get_ref_type(package="a.b", imports=imports, source_type="p.q.Message")
 
-    assert imports == {"from ...p import q as __p_q"}
-    assert name == "__p_q.Message"
+    assert imports == {"from ...p import q as __p_q__"}
+    assert name == "__p_q__.Message"
 
 
 def test_import_unrelated_deeply_nested_package():
@@ -242,16 +242,16 @@ def test_import_unrelated_deeply_nested_package():
         package="a.b.c.d", imports=imports, source_type="p.q.r.s.Message"
     )
 
-    assert imports == {"from .....p.q.r import s as ____p_q_r_s"}
-    assert name == "____p_q_r_s.Message"
+    assert imports == {"from .....p.q.r import s as ____p_q_r_s__"}
+    assert name == "____p_q_r_s__.Message"
 
 
 def test_import_cousin_package():
     imports = set()
     name = get_ref_type(package="a.x", imports=imports, source_type="a.y.Message")
 
-    assert imports == {"from .. import y as _y"}
-    assert name == "_y.Message"
+    assert imports == {"from .. import y as _y__"}
+    assert name == "_y__.Message"
 
 
 def test_import_cousin_package_different_name():
@@ -260,8 +260,8 @@ def test_import_cousin_package_different_name():
         package="test.package1", imports=imports, source_type="cousin.package2.Message"
     )
 
-    assert imports == {"from ...cousin import package2 as __cousin_package2"}
-    assert name == "__cousin_package2.Message"
+    assert imports == {"from ...cousin import package2 as __cousin_package2__"}
+    assert name == "__cousin_package2__.Message"
 
 
 def test_import_cousin_package_same_name():
@@ -270,16 +270,16 @@ def test_import_cousin_package_same_name():
         package="test.package", imports=imports, source_type="cousin.package.Message"
     )
 
-    assert imports == {"from ...cousin import package as __cousin_package"}
-    assert name == "__cousin_package.Message"
+    assert imports == {"from ...cousin import package as __cousin_package__"}
+    assert name == "__cousin_package__.Message"
 
 
 def test_import_far_cousin_package():
     imports = set()
     name = get_ref_type(package="a.x.y", imports=imports, source_type="a.b.c.Message")
 
-    assert imports == {"from ...b import c as __b_c"}
-    assert name == "__b_c.Message"
+    assert imports == {"from ...b import c as __b_c__"}
+    assert name == "__b_c__.Message"
 
 
 def test_import_far_far_cousin_package():
@@ -288,8 +288,8 @@ def test_import_far_far_cousin_package():
         package="a.x.y.z", imports=imports, source_type="a.b.c.d.Message"
     )
 
-    assert imports == {"from ....b.c import d as ___b_c_d"}
-    assert name == "___b_c_d.Message"
+    assert imports == {"from ....b.c import d as ___b_c_d__"}
+    assert name == "___b_c_d__.Message"
 
 
 @pytest.mark.parametrize(