diff --git a/src/ui/TDiagramPanel.java b/src/ui/TDiagramPanel.java
index 1275027c9665716e04fa40ae6d6c65aab159edb9..ee91598df8786251571d2ebc3bc54bde27eca20d 100755
--- a/src/ui/TDiagramPanel.java
+++ b/src/ui/TDiagramPanel.java
@@ -1840,8 +1840,10 @@ public abstract class TDiagramPanel extends JPanel implements GenericTree {
         
         if (componentPointed instanceof CheckableInvariant){
             checkInvariant.setEnabled(true);
+            checkMasterMutex.setEnabled(true);
         } else {
             checkInvariant.setEnabled(false);
+            checkMasterMutex.setEnabled(false);
         }
 		
 		if (componentPointed instanceof AllowedBreakpoint){
diff --git a/src/ui/sd/SDInstance.java b/src/ui/sd/SDInstance.java
index 7216086f9ae5b1f6ebca67df269b81e197a267df..cf5d50a28ad031c86a98ac4c6f1e11a013755845 100755
--- a/src/ui/sd/SDInstance.java
+++ b/src/ui/sd/SDInstance.java
@@ -152,7 +152,7 @@ public class SDInstance extends TGCWithInternalComponent implements SwallowTGCom
     }
     
     public int getMyCurrentMinY() {
-        return Math.min(y-hText, y);
+        return Math.min(y-hText-heightActor, y);
     }
     
     public String getInstanceName() {