diff --git a/masque/file/dxf.py b/masque/file/dxf.py
index 906fc2f..f99455b 100644
--- a/masque/file/dxf.py
+++ b/masque/file/dxf.py
@@ -70,7 +70,7 @@ def write(pattern: Pattern,
     """
     #TODO consider supporting DXF arcs?
     if disambiguate_func is None:
-        disambiguate_func = disambiguate_pattern_names
+        disambiguate_func = lambda pats: disambiguate_pattern_names(pats)
     assert(disambiguate_func is not None)
 
     if not modify_originals:
@@ -349,7 +349,7 @@ def _mlayer2dxf(layer: layer_t) -> str:
     raise PatternError(f'Unknown layer type: {layer} ({type(layer)})')
 
 
-def disambiguate_pattern_names(patterns: Sequence[Pattern],
+def disambiguate_pattern_names(patterns: Iterable[Pattern],
                                max_name_length: int = 32,
                                suffix_length: int = 6,
                                dup_warn_filter: Callable[[str], bool] = None,      # If returns False, don't warn about this name
diff --git a/masque/file/oasis.py b/masque/file/oasis.py
index dea703d..92abbfd 100644
--- a/masque/file/oasis.py
+++ b/masque/file/oasis.py
@@ -674,7 +674,7 @@ def annotations_to_properties(annotations: annotations_t) -> List[fatrec.Propert
     for key, values in annotations.items():
         vals = [AString(v) if isinstance(v, str) else v
                 for v in values]
-        properties.append(fatrec.Property(key, vals, is_standard=False))
+        properties.append(fatrec.Property(key, vals, is_standard=False))        # type: ignore
     return properties
 
 
diff --git a/masque/label.py b/masque/label.py
index b436653..d71d69c 100644
--- a/masque/label.py
+++ b/masque/label.py
@@ -58,11 +58,11 @@ class Label(PositionableImpl, LayerableImpl, LockableImpl, RepeatableImpl, Annot
         self.set_locked(locked)
 
     def __copy__(self: L) -> L:
-        return Label(string=self.string,
-                     offset=self.offset.copy(),
-                     layer=self.layer,
-                     repetition=self.repetition,
-                     locked=self.locked)
+        return type(self)(string=self.string,
+                          offset=self.offset.copy(),
+                          layer=self.layer,
+                          repetition=self.repetition,
+                          locked=self.locked)
 
     def __deepcopy__(self: L, memo: Dict = None) -> L:
         memo = {} if memo is None else memo
diff --git a/masque/pattern.py b/masque/pattern.py
index 2dcd9c6..7cbd06d 100644
--- a/masque/pattern.py
+++ b/masque/pattern.py
@@ -2,7 +2,7 @@
  Base object representing a lithography mask.
 """
 
-from typing import List, Callable, Tuple, Dict, Union, Set, Sequence, Optional, Type, overload
+from typing import List, Callable, Tuple, Dict, Union, Set, Sequence, Optional, Type, overload, cast
 from typing import MutableMapping, Iterable, TypeVar, Any
 import copy
 import pickle
@@ -18,7 +18,8 @@ from .shapes import Shape, Polygon
 from .label import Label
 from .utils import rotation_matrix_2d, vector2, normalize_mirror, AutoSlots, annotations_t
 from .error import PatternError, PatternLockedError
-from .traits import LockableImpl, AnnotatableImpl, Scalable
+from .traits import LockableImpl, AnnotatableImpl, Scalable, Mirrorable
+from .traits import Rotatable, Positionable
 
 
 visitor_function_t = Callable[['Pattern', Tuple['Pattern'], Dict, numpy.ndarray], 'Pattern']
@@ -27,7 +28,7 @@ visitor_function_t = Callable[['Pattern', Tuple['Pattern'], Dict, numpy.ndarray]
 P = TypeVar('P', bound='Pattern')
 
 
-class Pattern(LockableImpl, AnnotatableImpl, metaclass=AutoSlots):
+class Pattern(LockableImpl, AnnotatableImpl, Mirrorable, metaclass=AutoSlots):
     """
     2D layout consisting of some set of shapes, labels, and references to other Pattern objects
      (via SubPattern). Shapes are assumed to inherit from masque.shapes.Shape or provide equivalent functions.
@@ -710,7 +711,7 @@ class Pattern(LockableImpl, AnnotatableImpl, metaclass=AutoSlots):
             self
         """
         for entry in chain(self.shapes, self.subpatterns):
-            entry.rotate(rotation)
+            cast(Rotatable, entry).rotate(rotation)
         return self
 
     def mirror_element_centers(self: P, axis: int) -> P:
@@ -741,7 +742,7 @@ class Pattern(LockableImpl, AnnotatableImpl, metaclass=AutoSlots):
             self
         """
         for entry in chain(self.shapes, self.subpatterns):
-            entry.mirror(axis)
+            cast(Mirrorable, entry).mirror(axis)
         return self
 
     def mirror(self: P, axis: int) -> P:
@@ -856,7 +857,7 @@ class Pattern(LockableImpl, AnnotatableImpl, metaclass=AutoSlots):
         """
         self.lock()
         for ss in chain(self.shapes, self.labels):
-            ss.lock()
+            ss.lock()       # type: ignore      # mypy struggles with multiple inheritance :(
         for sp in self.subpatterns:
             sp.deeplock()
         return self
@@ -873,7 +874,7 @@ class Pattern(LockableImpl, AnnotatableImpl, metaclass=AutoSlots):
         """
         self.unlock()
         for ss in chain(self.shapes, self.labels):
-            ss.unlock()
+            ss.unlock()       # type: ignore      # mypy struggles with multiple inheritance :(
         for sp in self.subpatterns:
             sp.deepunlock()
         return self
diff --git a/masque/subpattern.py b/masque/subpattern.py
index 89e143e..1d5fb41 100644
--- a/masque/subpattern.py
+++ b/masque/subpattern.py
@@ -79,7 +79,7 @@ class SubPattern(PositionableImpl, DoseableImpl, RotatableImpl, ScalableImpl, Mi
         self.dose = dose
         self.scale = scale
         if mirrored is None:
-            mirrored = [False, False]
+            mirrored = (False, False)
         self.mirrored = mirrored
         self.repetition = repetition
         self.annotations = annotations if annotations is not None else {}