diff --git a/src/addons/transitions/ReactTransitionGroup.js b/src/addons/transitions/ReactTransitionGroup.js
index f77f63a1cd34d..a29dc3d2c2131 100644
--- a/src/addons/transitions/ReactTransitionGroup.js
+++ b/src/addons/transitions/ReactTransitionGroup.js
@@ -119,7 +119,7 @@ var ReactTransitionGroup = React.createClass({
       this.props.children
     );
 
-    if (!currentChildMapping.hasOwnProperty(key)) {
+    if (!currentChildMapping || !currentChildMapping.hasOwnProperty(key)) {
       // This was removed before it had fully entered. Remove it.
       this.performLeave(key);
     }
@@ -152,7 +152,7 @@ var ReactTransitionGroup = React.createClass({
       this.props.children
     );
 
-    if (currentChildMapping.hasOwnProperty(key)) {
+    if (currentChildMapping && currentChildMapping.hasOwnProperty(key)) {
       // This entered again before it fully left. Add it again.
       this.performEnter(key);
     } else {