diff --git a/src/core/ReactComponent.js b/src/core/ReactComponent.js
index 67b4e90207..530a6f9c66 100644
--- a/src/core/ReactComponent.js
+++ b/src/core/ReactComponent.js
@@ -58,10 +58,12 @@ var ComponentLifeCycle = keyMirror({
  */
 
 var CHILD_HAS_NO_IDENTITY =
-    'You are passing a dynamic array of children. You should set the ' +
-    'property "key" to a string that uniquely identifies each child.';
+  'Each child in an array should have a unique "key" prop. ' +
+  'Check the render method of ';
 
-var HAS_WARNED = false;
+var CHILD_CAME_FROM_ANOTHER_OWNER = '. It was passed a child from ';
+
+var owner_has_warned = {};
 
 /**
  * Helpers for flattening child arguments onto a new array or use an existing
@@ -108,9 +110,28 @@ function assignKey(groupingIndex, child, index) {
       // This is in an array. This could grow and shrink or be reordered.
       // All children that doesn't already have autogenerated identity needs
       // to have an explicit key provided.
-      if (!HAS_WARNED && key == null) {
-        HAS_WARNED = true;
-        console && console.warn && console.warn(CHILD_HAS_NO_IDENTITY);
+      if (key == null) {
+        // Name of the component whose render method tried to pass children.
+        var currentName =
+          ReactCurrentOwner.current &&
+          ReactCurrentOwner.current.constructor.displayName;
+
+        // Name of the component that originally created this child.
+        var childOwnerName =
+          child.props[OWNER] && child.props[OWNER].constructor.displayName;
+
+        if (currentName && !owner_has_warned.hasOwnProperty(currentName)) {
+          owner_has_warned[currentName] = true;
+          var message = CHILD_HAS_NO_IDENTITY + currentName;
+          if (childOwnerName && currentName !== childOwnerName) {
+            // Usually the current owner is the offender, but if it accepts
+            // children as a property, it may be the creator of the child that's
+            // responsible for assigning it a key.
+            message += CHILD_CAME_FROM_ANOTHER_OWNER + childOwnerName;
+          }
+          message += '.';
+          console && console.warn && console.warn(message);
+        }
       }
     }
     child._key = createKey(key, index, groupingIndex);