diff --git a/masque/label.py b/masque/label.py
index fe2c8cb..390ca84 100644
--- a/masque/label.py
+++ b/masque/label.py
@@ -49,7 +49,7 @@ class Label:
 
         if val.size != 2:
             raise PatternError('Offset must be convertible to size-2 ndarray')
-        self._offset = val.flatten()
+        self._offset = val.flatten().astype(float)
 
     # layer property
     @property
@@ -83,7 +83,7 @@ class Label:
         self.unlock()
         self.identifier = ()
         self.string = string
-        self.offset = numpy.array(offset, dtype=float)
+        self.offset = numpy.array(offset, dtype=float, copy=True)
         self.layer = layer
         self.locked = locked
 
diff --git a/masque/repetition.py b/masque/repetition.py
index 11833c5..47c4370 100644
--- a/masque/repetition.py
+++ b/masque/repetition.py
@@ -225,7 +225,7 @@ class GridRepetition:
     def mirrored(self, val: List[bool]):
         if is_scalar(val):
             raise PatternError('Mirrored must be a 2-element list of booleans')
-        self._mirrored = numpy.array(val, dtype=bool)
+        self._mirrored = numpy.array(val, dtype=bool, copy=True)
 
     # a_vector property
     @property
@@ -239,7 +239,7 @@ class GridRepetition:
 
         if val.size != 2:
             raise PatternError('a_vector must be convertible to size-2 ndarray')
-        self._a_vector = val.flatten()
+        self._a_vector = val.flatten().astype(float)
 
     # b_vector property
     @property
@@ -249,7 +249,7 @@ class GridRepetition:
     @b_vector.setter
     def b_vector(self, val: vector2):
         if not isinstance(val, numpy.ndarray):
-            val = numpy.array(val, dtype=float)
+            val = numpy.array(val, dtype=float, copy=True)
 
         if val.size != 2:
             raise PatternError('b_vector must be convertible to size-2 ndarray')
diff --git a/masque/shapes/path.py b/masque/shapes/path.py
index bd24bdf..85aafc3 100644
--- a/masque/shapes/path.py
+++ b/masque/shapes/path.py
@@ -98,7 +98,7 @@ class Path(Shape):
 
     @vertices.setter
     def vertices(self, val: numpy.ndarray):
-        val = numpy.array(val, dtype=float)
+        val = numpy.array(val, dtype=float)                 #TODO document that these might not be copied
         if len(val.shape) < 2 or val.shape[1] != 2:
             raise PatternError('Vertices must be an Nx2 array')
         if val.shape[0] < 2:
diff --git a/masque/shapes/polygon.py b/masque/shapes/polygon.py
index 67c9fdd..4bd8384 100644
--- a/masque/shapes/polygon.py
+++ b/masque/shapes/polygon.py
@@ -30,7 +30,7 @@ class Polygon(Shape):
 
     @vertices.setter
     def vertices(self, val: numpy.ndarray):
-        val = numpy.array(val, dtype=float)
+        val = numpy.array(val, dtype=float)                  #TODO document that these might not be copied
         if len(val.shape) < 2 or val.shape[1] != 2:
             raise PatternError('Vertices must be an Nx2 array')
         if val.shape[0] < 3:
diff --git a/masque/shapes/text.py b/masque/shapes/text.py
index 8db7c4a..684c637 100644
--- a/masque/shapes/text.py
+++ b/masque/shapes/text.py
@@ -64,7 +64,7 @@ class Text(Shape):
     def mirrored(self, val: List[bool]):
         if is_scalar(val):
             raise PatternError('Mirrored must be a 2-element list of booleans')
-        self._mirrored = list(val)
+        self._mirrored = numpy.ndarray(val, dtype=bool, copy=True)
 
     def __init__(self,
                  string: str,
diff --git a/masque/subpattern.py b/masque/subpattern.py
index 55d1ef1..1bb926c 100644
--- a/masque/subpattern.py
+++ b/masque/subpattern.py
@@ -153,7 +153,7 @@ class SubPattern:
     def mirrored(self, val: List[bool]):
         if is_scalar(val):
             raise PatternError('Mirrored must be a 2-element list of booleans')
-        self._mirrored = numpy.array(val, dtype=bool)
+        self._mirrored = numpy.array(val, dtype=bool, copy=True)
 
     def as_pattern(self) -> 'Pattern':
         """