diff --git a/src/main/java/de/neemann/digital/core/Model.java b/src/main/java/de/neemann/digital/core/Model.java
index 63d0a3b2f..2a4574bb0 100644
--- a/src/main/java/de/neemann/digital/core/Model.java
+++ b/src/main/java/de/neemann/digital/core/Model.java
@@ -75,6 +75,7 @@ public class Model implements Iterable<Node>, SyncAccess {
     private boolean isInvalidSignal = false;
     private AsyncSeq asyncInfos;
     private boolean asyncMode = false;
+    private boolean allowGlobalValues = false;
 
     private final ArrayList<ModelStateObserver> observers;
     private ArrayList<ModelStateObserver> observersStep;
@@ -740,6 +741,27 @@ public class Model implements Iterable<Node>, SyncAccess {
         return null;
     }
 
+    /**
+     * Registers a global value.
+     *
+     * @param name  the name
+     * @param value the value
+     */
+    public void registerGlobalValue(String name, ObservableValue value) {
+        if (allowGlobalValues)
+            GlobalValues.getInstance().register(name, value, this);
+    }
+
+    /**
+     * Set or denies the creation of global values.
+     *
+     * @param allowGlobalValues if true, global values are published
+     * @return this for chained calls
+     */
+    public Model setAllowGlobalValues(boolean allowGlobalValues) {
+        this.allowGlobalValues = allowGlobalValues;
+        return this;
+    }
 
     /**
      * Sets async execution infos
diff --git a/src/main/java/de/neemann/digital/core/io/Probe.java b/src/main/java/de/neemann/digital/core/io/Probe.java
index e83b8c9e0..27b9deeb2 100644
--- a/src/main/java/de/neemann/digital/core/io/Probe.java
+++ b/src/main/java/de/neemann/digital/core/io/Probe.java
@@ -54,7 +54,7 @@ public class Probe implements Element {
     @Override
     public void registerNodes(Model model) {
         model.addSignal(new Signal(label, value).setFormat(format));
-        GlobalValues.getInstance().register(label, value, model);
+        model.registerGlobalValue(label, value);
     }
 
 }
diff --git a/src/main/java/de/neemann/digital/draw/model/ModelCreator.java b/src/main/java/de/neemann/digital/draw/model/ModelCreator.java
index 9eb182f47..1683350e2 100644
--- a/src/main/java/de/neemann/digital/draw/model/ModelCreator.java
+++ b/src/main/java/de/neemann/digital/draw/model/ModelCreator.java
@@ -269,7 +269,7 @@ public class ModelCreator implements Iterable<ModelEntry> {
      * @throws NodeException NodeException
      */
     public Model createModel(boolean attachWires) throws PinException, NodeException {
-        Model m = new Model();
+        Model m = new Model().setAllowGlobalValues(attachWires);
 
         for (Net n : netList)
             n.interconnect(m, attachWires);