diff --git a/src/main/java/org/apposed/appose/NDArray.java b/src/main/java/org/apposed/appose/NDArray.java
index e86084b..7e0bdde 100644
--- a/src/main/java/org/apposed/appose/NDArray.java
+++ b/src/main/java/org/apposed/appose/NDArray.java
@@ -43,7 +43,7 @@ public class NDArray implements AutoCloseable {
 	/**
 	 * shared memory containing the flattened array data.
 	 */
-	private final SharedMemory sharedMemory;
+	private final SharedMemory shm;
 
 	/**
 	 * data type of the array elements.
@@ -56,16 +56,19 @@ public class NDArray implements AutoCloseable {
 	private final Shape shape;
 
 	/**
-	 * Constructs an {@code NDArray} with the specified {@code SharedMemory}.
+	 * Constructs an {@code NDArray} with the specified data type, shape,
+	 * and {@code SharedMemory}.
 	 *
-	 * @param sharedMemory the flattened array data.
 	 * @param dType element data type
 	 * @param shape array shape
+	 * @param shm the flattened array data.
 	 */
-	public NDArray(final SharedMemory sharedMemory, final DType dType, final Shape shape) {
-		this.sharedMemory = sharedMemory;
+	public NDArray(final DType dType, final Shape shape, final SharedMemory shm) {
 		this.dType = dType;
 		this.shape = shape;
+		this.shm = shm == null
+			? SharedMemory.create(null, safeInt(shape.numElements() * dType.bytesPerElement()))
+			: shm;
 	}
 
 	/**
@@ -76,8 +79,7 @@ public NDArray(final SharedMemory sharedMemory, final DType dType, final Shape s
 	 * @param shape array shape
 	 */
 	public NDArray(final DType dType, final Shape shape) {
-		this(SharedMemory.create(null,
-			safeInt(shape.numElements() * dType.bytesPerElement())), dType, shape);
+		this(dType, shape, null);
 	}
 
 	/**
@@ -98,7 +100,7 @@ public Shape shape() {
 	 * @return The shared memory block containing the array data.
 	 */
 	public SharedMemory shm() {
-		return sharedMemory;
+		return shm;
 	}
 
 	/**
@@ -108,7 +110,7 @@ public SharedMemory shm() {
 	 */
 	public ByteBuffer buffer() {
 		final long length = shape.numElements() * dType.bytesPerElement();
-		return sharedMemory.pointer().getByteBuffer(0, length);
+		return shm.pointer().getByteBuffer(0, length);
 	}
 
 	/**
@@ -116,16 +118,16 @@ public ByteBuffer buffer() {
 	 */
 	@Override
 	public void close() throws Exception {
-		sharedMemory.close();
+		shm.close();
 	}
 
 	@Override
 	public String toString() {
-		return "NDArray{" +
-				"sharedMemory=" + sharedMemory +
-				", dType=" + dType +
-				", shape=" + shape +
-				'}';
+		return "NDArray(" +
+			"dType=" + dType +
+			", shape=" + shape +
+			", shm=" + shm +
+			")";
 	}
 
 	/**
diff --git a/src/main/java/org/apposed/appose/Types.java b/src/main/java/org/apposed/appose/Types.java
index 811ff0c..f89bae4 100644
--- a/src/main/java/org/apposed/appose/Types.java
+++ b/src/main/java/org/apposed/appose/Types.java
@@ -132,9 +132,9 @@ public Object convert(final Object value, final String key) {
 				map.put("name", shm.name());
 				map.put("size", shm.size());
 			})).addConverter(convert(NDArray.class, "ndarray", (map, ndArray) -> {
-				map.put("shm", ndArray.shm());
 				map.put("dtype", ndArray.dType().label());
 				map.put("shape", ndArray.shape().toIntArray(C_ORDER));
+				map.put("shm", ndArray.shm());
 			})).build();
 
 
@@ -163,10 +163,10 @@ private static Object processValue(Object value) {
 						final int size = (int) map.get("size");
 						return SharedMemory.attach(name, size);
 					case "ndarray":
-						final SharedMemory shm = (SharedMemory) map.get("shm");
 						final NDArray.DType dType = toDType((String) map.get("dtype"));
 						final NDArray.Shape shape = toShape((List<Integer>) map.get("shape"));
-						return new NDArray(shm, dType, shape);
+						final SharedMemory shm = (SharedMemory) map.get("shm");
+						return new NDArray(dType, shape, shm);
 					default:
 						System.err.println("unknown appose_type \"" + appose_type + "\"");
 				}
diff --git a/src/test/java/org/apposed/appose/NDArrayExampleGroovy.java b/src/test/java/org/apposed/appose/NDArrayExampleGroovy.java
index 1467656..0948605 100644
--- a/src/test/java/org/apposed/appose/NDArrayExampleGroovy.java
+++ b/src/test/java/org/apposed/appose/NDArrayExampleGroovy.java
@@ -13,7 +13,8 @@ public static void main(String[] args) throws Exception {
 		// create a FLOAT32 NDArray with shape (4,3,2) in F_ORDER
 		// respectively (2,3,4) in C_ORDER
 		final NDArray.DType dType = NDArray.DType.FLOAT32;
-		final NDArray ndArray = new NDArray(dType, new NDArray.Shape(F_ORDER, 4, 3, 2));
+		final NDArray.Shape shape = new NDArray.Shape(F_ORDER, 4, 3, 2);
+		final NDArray ndArray = new NDArray(dType, shape);
 
 		// fill with values 0..23 in flat iteration order
 		final FloatBuffer buf = ndArray.buffer().asFloatBuffer();
diff --git a/src/test/java/org/apposed/appose/NDArrayExamplePython.java b/src/test/java/org/apposed/appose/NDArrayExamplePython.java
index 4a80b39..4512377 100644
--- a/src/test/java/org/apposed/appose/NDArrayExamplePython.java
+++ b/src/test/java/org/apposed/appose/NDArrayExamplePython.java
@@ -13,7 +13,8 @@ public static void main(String[] args) throws Exception {
 		// create a FLOAT32 NDArray with shape (4,3,2) in F_ORDER
 		// respectively (2,3,4) in C_ORDER
 		final NDArray.DType dType = NDArray.DType.FLOAT32;
-		final NDArray ndArray = new NDArray(dType, new NDArray.Shape(F_ORDER, 4, 3, 2));
+		final NDArray.Shape shape = new NDArray.Shape(F_ORDER, 4, 3, 2);
+		final NDArray ndArray = new NDArray(dType, shape);
 
 		// fill with values 0..23 in flat iteration order
 		final FloatBuffer buf = ndArray.buffer().asFloatBuffer();