Index: trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java	(revision 14677)
+++ trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java	(revision 14678)
@@ -1114,7 +1114,7 @@
         @Override
         public void actionPerformed(ActionEvent e) {
-            if (isPerforming.get())
+            if (!/*successful*/isPerforming.compareAndSet(false, true)) {
                 return;
-            isPerforming.set(true);
+            }
             try {
                 editHelper.addTag();
@@ -1140,7 +1140,7 @@
         @Override
         public void actionPerformed(ActionEvent e) {
-            if (isPerforming.get())
+            if (!/*successful*/isPerforming.compareAndSet(false, true)) {
                 return;
-            isPerforming.set(true);
+            }
             try {
                 if (tagTable.getSelectedRowCount() == 1) {