diff --git a/src/java/com/threerings/presents/dobj/AttributeChangedEvent.java b/src/java/com/threerings/presents/dobj/AttributeChangedEvent.java
index 8fc1a2b6e..3d7c14fef 100644
--- a/src/java/com/threerings/presents/dobj/AttributeChangedEvent.java
+++ b/src/java/com/threerings/presents/dobj/AttributeChangedEvent.java
@@ -21,6 +21,8 @@
 
 package com.threerings.presents.dobj;
 
+import java.util.HashMap;
+
 import com.samskivert.util.StringUtil;
 
 /**
@@ -114,9 +116,24 @@ public class AttributeChangedEvent extends NamedEvent
         // actually apply the attribute change
         if (_oldValue == UNSET_OLD_VALUE) {
             _oldValue = target.getAttribute(_name);
-            // pass the new value on to the object (this uses reflection
-            // and is slow)
-            target.setAttribute(_name, _value);
+            Object value = _value;
+            if (value != null) {
+                Class vclass = value.getClass();
+                if (vclass.isPrimitive()) {
+                    // do nothing; we check this to avoid the more
+                    // expensive isAssignableFrom check on primitives
+                    // which are far and away the most common case
+                } else if (vclass.isArray()) {
+                    Cloner cloner = (Cloner)_cloners.get(vclass);
+                    if (cloner != null) {
+                        value = cloner.clone(value);
+                    }
+                } else if (DSet.class.isAssignableFrom(vclass)) {
+                    value = ((DSet)value).clone();
+                }
+            }
+            // pass the new value on to the object
+            target.setAttribute(_name, value);
         }
         return true;
     }
@@ -160,6 +177,66 @@ public class AttributeChangedEvent extends NamedEvent
         StringUtil.toString(buf, _value);
     }
 
+    /** Used to clone object attributes without a zillion calls to
+     * instanceof. */
+    protected static interface Cloner {
+        public Object clone (Object object);
+    }
+
     protected Object _value;
     protected transient Object _oldValue = UNSET_OLD_VALUE;
+
+    /** Contains {@link Cloner}s for types that need cloning. */
+    protected static HashMap _cloners = new HashMap();
+
+    /** Object prototypes we can use to get the appropriate class objects
+     * for use when setting up {@link #_cloners}. */
+    protected static final Object[] ARRAY_PROTOS = new Object[] {
+        new String[0], new byte[0], new char[0], new short[0], new int[0],
+        new long[0], new float[0], new double[0]
+    };
+
+    // set up our cloners
+    static {
+        _cloners.put(ARRAY_PROTOS[0], new Cloner() {
+            public Object clone (Object obj) {
+                return ((String[])obj).clone();
+            }
+        });
+        _cloners.put(ARRAY_PROTOS[1], new Cloner() {
+            public Object clone (Object obj) {
+                return ((byte[])obj).clone();
+            }
+        });
+        _cloners.put(ARRAY_PROTOS[2], new Cloner() {
+            public Object clone (Object obj) {
+                return ((char[])obj).clone();
+            }
+        });
+        _cloners.put(ARRAY_PROTOS[3], new Cloner() {
+            public Object clone (Object obj) {
+                return ((short[])obj).clone();
+            }
+        });
+        _cloners.put(ARRAY_PROTOS[4], new Cloner() {
+            public Object clone (Object obj) {
+                return ((int[])obj).clone();
+            }
+        });
+        _cloners.put(ARRAY_PROTOS[5], new Cloner() {
+            public Object clone (Object obj) {
+                return ((long[])obj).clone();
+            }
+        });
+        _cloners.put(ARRAY_PROTOS[6], new Cloner() {
+            public Object clone (Object obj) {
+                return ((float[])obj).clone();
+            }
+        });
+        _cloners.put(ARRAY_PROTOS[7], new Cloner() {
+            public Object clone (Object obj) {
+                return ((double[])obj).clone();
+            }
+        });
+    }
 }
diff --git a/src/java/com/threerings/presents/tools/GenDObjectTask.java b/src/java/com/threerings/presents/tools/GenDObjectTask.java
index b17ac440e..8d5aa9e73 100644
--- a/src/java/com/threerings/presents/tools/GenDObjectTask.java
+++ b/src/java/com/threerings/presents/tools/GenDObjectTask.java
@@ -259,6 +259,8 @@ public class GenDObjectTask extends Task
             ctx.put("type", GenUtil.simpleName(ftype));
             ctx.put("wrapfield", GenUtil.boxArgument(ftype, "value"));
             ctx.put("wrapofield", GenUtil.boxArgument(ftype, "ovalue"));
+            ctx.put("clonefield",
+                    GenUtil.cloneArgument(_dsclass, ftype, "value"));
             ctx.put("capfield", StringUtil.unStudlyName(fname).toUpperCase());
             ctx.put("upfield", StringUtils.capitalize(fname));
             if (ftype.isArray()) {
diff --git a/src/java/com/threerings/presents/tools/GenUtil.java b/src/java/com/threerings/presents/tools/GenUtil.java
index 20cf9b0e0..fed91894f 100644
--- a/src/java/com/threerings/presents/tools/GenUtil.java
+++ b/src/java/com/threerings/presents/tools/GenUtil.java
@@ -116,6 +116,19 @@ public class GenUtil
         }
     }
 
+    /**
+     * Potentially clones the supplied argument if it is the type that
+     * needs such treatment.
+     */
+    public static String cloneArgument (Class dsclazz, Class clazz, String name)
+    {
+        if (clazz.isArray() || dsclazz.isAssignableFrom(clazz)) {
+            return "(" + simpleName(clazz) + ")" + name + ".clone()";
+        } else {
+            return name;
+        }
+    }
+
     /**
      * Reads in the supplied source file and locates the package and class
      * or interface name and returns a fully qualified class name.
diff --git a/src/java/com/threerings/presents/tools/dobject_field.tmpl b/src/java/com/threerings/presents/tools/dobject_field.tmpl
index e40f99b62..d48a4d7a1 100644
--- a/src/java/com/threerings/presents/tools/dobject_field.tmpl
+++ b/src/java/com/threerings/presents/tools/dobject_field.tmpl
@@ -11,7 +11,7 @@
         $type ovalue = this.$field;
         requestAttributeChange(
             $capfield, $wrapfield, $wrapofield);
-        this.$field = value;
+        this.$field = $clonefield;
     }
 #if ($elemtype)
 
diff --git a/src/java/com/threerings/presents/tools/dobject_set.tmpl b/src/java/com/threerings/presents/tools/dobject_set.tmpl
index 6f59db43a..7afe8063c 100644
--- a/src/java/com/threerings/presents/tools/dobject_set.tmpl
+++ b/src/java/com/threerings/presents/tools/dobject_set.tmpl
@@ -38,8 +38,8 @@
      * change. Proxied copies of this object (on clients) will apply the
      * value change when they received the attribute changed notification.
      */
-    public void set$upfield ($type $field)
+    public void set$upfield ($type value)
     {
-        requestAttributeChange($capfield, $field, this.$field);
-        this.$field = $field;
+        requestAttributeChange($capfield, value, this.$field);
+        this.$field = $clonefield;
     }