diff --git a/static/js/graphing.js b/static/js/graphing.js
index bb776d816..ba371fba4 100644
--- a/static/js/graphing.js
+++ b/static/js/graphing.js
@@ -367,14 +367,23 @@ ImageHistoryTree.prototype.markPath_ = function(startingNode, isHighlighted) {
  * Sets the current tag displayed in the tree.
  */
 ImageHistoryTree.prototype.setTag_ = function(tagName) {
+    if (tagName == this.currentTag_) {
+      return;
+    }
+
+    var imageByDBID = this.imageByDBID_;
+   
     // Save the current tag.
+    var previousTagName = this.currentTag_;
     this.currentTag_ = tagName;
    
-    var imageByDBID = this.imageByDBID_;
-
     // Update the state of each existing node to no longer be highlighted.
-    if (this.currentImage_) {
-      var currentNode = imageByDBID[this.currentImage_.dbid];
+    var previousImage = this.findImage_(function(image) {
+      return image.tags.indexOf(previousTagName || '(no tag specified)') >= 0;
+    });
+
+    if (previousImage) {
+      var currentNode = imageByDBID[previousImage.dbid];
       this.markPath_(currentNode, false);
     }