diff --git a/javascript/TreeSelectorField.js b/javascript/TreeSelectorField.js
index 3467e79f9..0ec79d640 100755
--- a/javascript/TreeSelectorField.js
+++ b/javascript/TreeSelectorField.js
@@ -96,7 +96,11 @@ TreeDropdownField.prototype = {
 						break;
 					}
 				}
-			} 
+			}
+			
+			// This iframe stretching doesn't work with the greybox
+			if(this.iframeObj.id == 'GB_frame') return;
+			
 			var desiredHeight = Position.cumulativeOffset(this.itemTree)[1] + this.itemTree.offsetHeight + 2;
 			if(this.iframeObj && desiredHeight > this.iframeObj.offsetHeight) {
 				this.iframeObj.oldHeight = this.iframeObj.offsetHeight;