diff --git a/common/src/main/java/com/dtteam/dynamictrees/api/registry/AbstractRegistry.java b/common/src/main/java/com/dtteam/dynamictrees/api/registry/AbstractRegistry.java
index 6fe934816..c730973ce 100644
--- a/common/src/main/java/com/dtteam/dynamictrees/api/registry/AbstractRegistry.java
+++ b/common/src/main/java/com/dtteam/dynamictrees/api/registry/AbstractRegistry.java
@@ -188,9 +188,14 @@ public final void lock() {
         this.locked = true;
         this.dump();
 
-        // Run all of the on lock runnables and then clear them.
-        this.onLockRunnables.forEach(Runnable::run);
-        this.onLockRunnables.clear();
+        if (onLockRunnables.isEmpty()) {
+            return;
+        }
+
+        // Copy the onLockRunnables to prevent a ConcurrentModificationException
+        List<Runnable> current = new ArrayList<>(onLockRunnables);
+        onLockRunnables.clear();
+        current.forEach(Runnable::run);
     }
 
     /**