diff --git a/06_oop_in_st/exercises/4_inheritance_complex_valve/src/TankWithVolume.st b/06_oop_in_st/exercises/4_inheritance_complex_valve/src/TankWithVolume.st
index 69b53e7..5546e55 100644
--- a/06_oop_in_st/exercises/4_inheritance_complex_valve/src/TankWithVolume.st
+++ b/06_oop_in_st/exercises/4_inheritance_complex_valve/src/TankWithVolume.st
@@ -21,6 +21,7 @@ NAMESPACE FluidHandlingClass
                 currentVolume : REAL;
             END_VAR 
             _capacity := (currentVolume / volume) * 100;
+            Capacity := _capacity;
         END_METHOD
 
         METHOD PUBLIC OpenInlet 
diff --git a/06_oop_in_st/exercises/solution/src/TankWithVolume.st b/06_oop_in_st/exercises/solution/src/TankWithVolume.st
index eae50f3..1a5b9bb 100644
--- a/06_oop_in_st/exercises/solution/src/TankWithVolume.st
+++ b/06_oop_in_st/exercises/solution/src/TankWithVolume.st
@@ -19,6 +19,7 @@ NAMESPACE FluidHandlingInterfaces
                 currentVolume : REAL;
             END_VAR 
             _capacity := (currentVolume / volume) * 100;
+            Capacity := _capacity;
         END_METHOD
 
         METHOD PUBLIC OpenInlet