diff --git a/se/sics/mspsim/util/ControlUI.java b/se/sics/mspsim/util/ControlUI.java
index 673b315..f0c510b 100644
--- a/se/sics/mspsim/util/ControlUI.java
+++ b/se/sics/mspsim/util/ControlUI.java
@@ -99,6 +99,7 @@ public class ControlUI extends JPanel implements ActionListener {
     stepAction = new AbstractAction("Single Step") {
 	public void actionPerformed(ActionEvent e) {
 	  ControlUI.this.cpu.step();
+	  dui.updateRegs();
 	  dui.repaint();
 	  if (elfData != null && sourceViewer != null
 	      && sourceViewer.isVisible()) {
diff --git a/se/sics/mspsim/util/DebugUI.java b/se/sics/mspsim/util/DebugUI.java
index 9e28495..5b51bbe 100644
--- a/se/sics/mspsim/util/DebugUI.java
+++ b/se/sics/mspsim/util/DebugUI.java
@@ -98,6 +98,7 @@ public class DebugUI extends JPanel {
 	regsLabel[i].setText("$" + Utils.hex16(cpu.reg[i]));
       }
     }
+    repaint();
   }
 
   private class DbgListModel extends AbstractListModel {