diff --git a/CHANGELOG.md b/CHANGELOG.md
index d35f96af8..d39dc6b67 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -22,6 +22,7 @@ All notable changes to this project will be documented in this file.
 - Radial gradients focal point reading/writing
 - Correct AS/P-code matching in editor for AS3 after using deobfuscation
 - Correct line matching in debugger of AS3 after using deobfuscation
+- Concurrent access while in debugger
 
 ## [11.3.0] - 2020-04-25
 ### Added
diff --git a/src/com/jpexs/decompiler/flash/gui/DebuggerHandler.java b/src/com/jpexs/decompiler/flash/gui/DebuggerHandler.java
index 140fc80d6..d53955b93 100644
--- a/src/com/jpexs/decompiler/flash/gui/DebuggerHandler.java
+++ b/src/com/jpexs/decompiler/flash/gui/DebuggerHandler.java
@@ -59,6 +59,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.TreeSet;
+import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.logging.ConsoleHandler;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -330,7 +331,7 @@ public class DebuggerHandler implements DebugConnectionListener {
 
     private InBreakReason breakReason;
 
-    private final List<BreakListener> breakListeners = new ArrayList<>();
+    private final List<BreakListener> breakListeners = new CopyOnWriteArrayList<>();
 
     private final List<TraceListener> traceListeners = new ArrayList<>();