diff --git a/modules/ve/dm/ve.dm.Document.js b/modules/ve/dm/ve.dm.Document.js
index 80df2e5bbe..67430b94e4 100644
--- a/modules/ve/dm/ve.dm.Document.js
+++ b/modules/ve/dm/ve.dm.Document.js
@@ -8,6 +8,13 @@
 /**
  * DataModel document.
  *
+ * WARNING: Data passed into a new document will be sliced, creating a shallow copy. This is done to
+ * prevent multiple documents sharing references to the same data, which causes very strange and
+ * difficult to diagnose issues. By slicing by default, this issue is dealt with automatically. This
+ * comes at a price however. While a slice is much faster than a deep copy, it may still be a
+ * problem with really big data sets. We do not know that this is an issue yet, but consider it a
+ * likely area to cause performance problems in the future.
+ *
  * @class
  * @extends {ve.Document}
  * @constructor
@@ -20,7 +27,7 @@ ve.dm.Document = function ( data, parentDocument ) {
 
 	// Properties
 	this.parentDocument = parentDocument;
-	this.data = data || [];
+	this.data = ve.isArray( data ) ? data.slice( 0 ) : [];
 
 	// Initialization
 	/*
diff --git a/modules/ve/test/dm/ve.dm.Document.test.js b/modules/ve/test/dm/ve.dm.Document.test.js
index ddd150f47b..70a286f17c 100644
--- a/modules/ve/test/dm/ve.dm.Document.test.js
+++ b/modules/ve/test/dm/ve.dm.Document.test.js
@@ -898,7 +898,7 @@ QUnit.test( 'isContentData', 1, function ( assert ) {
 
 QUnit.test( 'rebuildNodes', function ( assert ) {
 	var tree,
-		doc = new ve.dm.Document( ve.dm.example.data.slice( 0 ) ),
+		doc = new ve.dm.Document( ve.dm.example.data ),
 		documentNode = doc.getDocumentNode();
 	// Rebuild table without changes
 	doc.rebuildNodes( documentNode, 1, 1, 5, 32 );
diff --git a/modules/ve/test/dm/ve.dm.DocumentSynchronizer.test.js b/modules/ve/test/dm/ve.dm.DocumentSynchronizer.test.js
index 937ad51b39..47e281150a 100644
--- a/modules/ve/test/dm/ve.dm.DocumentSynchronizer.test.js
+++ b/modules/ve/test/dm/ve.dm.DocumentSynchronizer.test.js
@@ -10,13 +10,13 @@ QUnit.module( 've.dm.DocumentSynchronizer' );
 /* Tests */
 
 QUnit.test( 'getDocument', 1, function ( assert ) {
-	var doc = new ve.dm.Document( ve.dm.example.data.slice( 0 ) ),
+	var doc = new ve.dm.Document( ve.dm.example.data ),
 		ds = new ve.dm.DocumentSynchronizer( doc );
 	assert.strictEqual( ds.getDocument(), doc );
 } );
 
 QUnit.test( 'synchronize', 2, function ( assert ) {
-	var doc = new ve.dm.Document( ve.dm.example.data.slice( 0 ) ),
+	var doc = new ve.dm.Document( ve.dm.example.data ),
 		ds = new ve.dm.DocumentSynchronizer( doc );
 
 	// Annotate "a" with bold formatting