diff --git a/kotlin/school-timetabling/src/main/kotlin/org/acme/kotlin/schooltimetabling/solver/TimeTableConstraintProvider.kt b/kotlin/school-timetabling/src/main/kotlin/org/acme/kotlin/schooltimetabling/solver/TimeTableConstraintProvider.kt
index 79a89e93f8..2db0a95b63 100644
--- a/kotlin/school-timetabling/src/main/kotlin/org/acme/kotlin/schooltimetabling/solver/TimeTableConstraintProvider.kt
+++ b/kotlin/school-timetabling/src/main/kotlin/org/acme/kotlin/schooltimetabling/solver/TimeTableConstraintProvider.kt
@@ -43,7 +43,7 @@ class TimeTableConstraintProvider : ConstraintProvider {
             // ... and penalize each pair with a hard weight.
             .penalize(HardSoftScore.ONE_HARD)
             .justifyWith { lesson1: Lesson, lesson2: Lesson, _ ->
-                RoomConflictJustification(lesson1.room, lesson1,lesson2)
+                RoomConflictJustification(lesson1.room!!, lesson1, lesson2)
             }
             .asConstraint("Room conflict")
     }
diff --git a/kotlin/school-timetabling/src/main/kotlin/org/acme/kotlin/schooltimetabling/solver/justifications/RoomConflictJustification.kt b/kotlin/school-timetabling/src/main/kotlin/org/acme/kotlin/schooltimetabling/solver/justifications/RoomConflictJustification.kt
index af5381d65c..1d913543b4 100644
--- a/kotlin/school-timetabling/src/main/kotlin/org/acme/kotlin/schooltimetabling/solver/justifications/RoomConflictJustification.kt
+++ b/kotlin/school-timetabling/src/main/kotlin/org/acme/kotlin/schooltimetabling/solver/justifications/RoomConflictJustification.kt
@@ -6,7 +6,7 @@ import org.acme.kotlin.schooltimetabling.domain.Room
 
 
 data class RoomConflictJustification(
-    val room: Room?,
+    val room: Room,
     val lesson1: Lesson,
     val lesson2: Lesson,
     val description: String
@@ -14,7 +14,7 @@ data class RoomConflictJustification(
     ConstraintJustification {
 
     constructor(
-        room: Room?,
+        room: Room,
         lesson1: Lesson,
         lesson2: Lesson
     ) : this(
diff --git a/kotlin/school-timetabling/src/test/kotlin/org/acme/kotlin/schooltimetabling/rest/TimetableEnvironmentTest.kt b/kotlin/school-timetabling/src/test/kotlin/org/acme/kotlin/schooltimetabling/rest/TimetableEnvironmentTest.kt
index b712a394a4..94f6f749d2 100644
--- a/kotlin/school-timetabling/src/test/kotlin/org/acme/kotlin/schooltimetabling/rest/TimetableEnvironmentTest.kt
+++ b/kotlin/school-timetabling/src/test/kotlin/org/acme/kotlin/schooltimetabling/rest/TimetableEnvironmentTest.kt
@@ -30,7 +30,7 @@ class TimetableEnvironmentTest {
         solve(EnvironmentMode.FAST_ASSERT)
     }
 
-    fun solve(environmentMode: EnvironmentMode?) {
+    fun solve(environmentMode: EnvironmentMode) {
         // Load the problem
         val problem: Timetable = given()
             .`when`()["/demo-data/SMALL"]
@@ -39,12 +39,10 @@ class TimetableEnvironmentTest {
             .extract()
             .`as`(Timetable::class.java)
 
-        // Update the environment
         // Update the environment
         val updatedConfig = solverConfig!!.copyConfig()
-        updatedConfig.withEnvironmentMode(environmentMode)
             .withTerminationSpentLimit(Duration.ofSeconds(30))
-            .terminationConfig.withBestScoreLimit(null)
+            .withEnvironmentMode(environmentMode)
         val solverFactory: SolverFactory<Timetable> = SolverFactory.create(updatedConfig)
 
         // Solve the problem