diff --git a/platform/platform-api/src/com/intellij/util/ui/update/MergingUpdateQueue.java b/platform/platform-api/src/com/intellij/util/ui/update/MergingUpdateQueue.java
index 2d53caf3d64b..71b117b56126 100644
--- a/platform/platform-api/src/com/intellij/util/ui/update/MergingUpdateQueue.java
+++ b/platform/platform-api/src/com/intellij/util/ui/update/MergingUpdateQueue.java
@@ -30,10 +30,10 @@ import org.jetbrains.annotations.Nullable;
 
 import javax.swing.*;
 import java.util.Map;
+import java.util.Set;
 import java.util.TreeMap;
 
 public class MergingUpdateQueue implements Runnable, Disposable, Activatable {
-
   public static final JComponent ANY_COMPONENT = new JComponent() {
   };
 
@@ -124,7 +124,8 @@ public class MergingUpdateQueue implements Runnable, Disposable, Activatable {
 
   public void cancelAllUpdates() {
     synchronized (myScheduledUpdates) {
-      for (Update each : myScheduledUpdates.keySet()) {
+      Update[] updates = myScheduledUpdates.keySet().toArray(new Update[myScheduledUpdates.size()]);
+      for (Update each : updates) {
         try {
           each.setRejected();
         }
@@ -400,7 +401,9 @@ public class MergingUpdateQueue implements Runnable, Disposable, Activatable {
 
   @SuppressWarnings({"HardCodedStringLiteral"})
   public String toString() {
-    return myName + " active=" + myActive + " scheduled=" + myScheduledUpdates.size();
+    synchronized (myScheduledUpdates) {
+      return myName + " active=" + myActive + " scheduled=" + myScheduledUpdates.size();
+    }
   }
 
   @Nullable