diff --git a/NumLib/TimeStepping/TimeInterval.h b/NumLib/TimeStepping/TimeInterval.h
index 13e492719fe616c2e30d2ec1e06118c734fe7b2f..0bf7658e102e52635c8002292dc49c2bd4fac9ea 100644
--- a/NumLib/TimeStepping/TimeInterval.h
+++ b/NumLib/TimeStepping/TimeInterval.h
@@ -18,7 +18,7 @@ namespace NumLib
  * Class for a time interval, which has a member to check whether the given time
  * is in this time interval.
  */
-class TimeInterval
+class TimeInterval final
 {
 public:
     TimeInterval(const double start_time, const double end_time)
@@ -26,11 +26,9 @@ public:
     {
     }
 
-    bool isInThisTimeInterval(const double current_time) const
+    bool contains(const double current_time) const
     {
-        return (current_time >= _start_time && current_time <= _end_time)
-                   ? true
-                   : false;
+        return (current_time >= _start_time && current_time <= _end_time);
     }
 
 private:
diff --git a/ProcessLib/BoundaryCondition/DirichletBoundaryCondition.cpp b/ProcessLib/BoundaryCondition/DirichletBoundaryCondition.cpp
index 938b6663d0a458c082e3c07abfb51e376198729a..8e3274407dee7965ce416aa0736eda8a49565a67 100644
--- a/ProcessLib/BoundaryCondition/DirichletBoundaryCondition.cpp
+++ b/ProcessLib/BoundaryCondition/DirichletBoundaryCondition.cpp
@@ -70,7 +70,7 @@ void DirichletBoundaryCondition::getEssentialBCValues(
     const double t, GlobalVector const& x,
     NumLib::IndexValueVector<GlobalIndexType>& bc_values) const
 {
-    return getEssentialBCValuesLocal(t, x, bc_values);
+    getEssentialBCValuesLocal(t, x, bc_values);
 }
 
 void DirichletBoundaryCondition::getEssentialBCValuesLocal(
diff --git a/ProcessLib/BoundaryCondition/DirichletBoundaryConditionWithinTimeInterval.cpp b/ProcessLib/BoundaryCondition/DirichletBoundaryConditionWithinTimeInterval.cpp
index e682e6f996f7e628312b1596c33aaf813edfea83..a1a338a5e69c7d3916fd3999c8a5d0ed93e8af0d 100644
--- a/ProcessLib/BoundaryCondition/DirichletBoundaryConditionWithinTimeInterval.cpp
+++ b/ProcessLib/BoundaryCondition/DirichletBoundaryConditionWithinTimeInterval.cpp
@@ -40,9 +40,10 @@ void DirichletBoundaryConditionWithinTimeInterval::getEssentialBCValues(
     const double t, GlobalVector const& x,
     NumLib::IndexValueVector<GlobalIndexType>& bc_values) const
 {
-    if (_time_interval->isInThisTimeInterval(t))
+    if (_time_interval->contains(t))
     {
-        return getEssentialBCValuesLocal(t, x, bc_values);
+        getEssentialBCValuesLocal(t, x, bc_values);
+        return;
     }
 
     bc_values.ids.clear();