diff --git a/src/main/java/com/loomcom/symon/Simulator.java b/src/main/java/com/loomcom/symon/Simulator.java
index d8e3686..128f3a4 100644
--- a/src/main/java/com/loomcom/symon/Simulator.java
+++ b/src/main/java/com/loomcom/symon/Simulator.java
@@ -364,6 +364,9 @@ public class Simulator {
 
         if (videoWindow != null && stepsSinceLastCrtcRefresh++ > stepsBetweenCrtcRefreshes) {
             stepsSinceLastCrtcRefresh = 0;
+            if (videoWindow.isVisible()) {
+                videoWindow.repaint();
+            }
         }
 
         // This is a very expensive update, and we're doing it without