diff --git a/theodolite/src/main/kotlin/theodolite/benchmark/Action.kt b/theodolite/src/main/kotlin/theodolite/benchmark/Action.kt
index 35efebdc0fb2a3748660cb76cdd5499b4ca5f622..8bd16d04d6a5e5ef3f362ff7d5611bf73e367a7e 100644
--- a/theodolite/src/main/kotlin/theodolite/benchmark/Action.kt
+++ b/theodolite/src/main/kotlin/theodolite/benchmark/Action.kt
@@ -23,7 +23,7 @@ class Action {
                 timeout = exec.timeoutSeconds,
                 command = exec.command
         )
-            if(exitCode != 0){
+        if (exitCode != 0){
             throw ActionCommandFailedException("Error while executing action, finished with exit code $exitCode")
         }
     }
@@ -38,7 +38,7 @@ class ActionSelector {
 @JsonDeserialize
 @RegisterForReflection
 class PodSelector {
-    lateinit var matchLabels: MutableMap<String, String>
+    lateinit var matchLabels: Map<String, String>
 }
 @JsonDeserialize
 @RegisterForReflection
diff --git a/theodolite/src/main/kotlin/theodolite/benchmark/ActionCommand.kt b/theodolite/src/main/kotlin/theodolite/benchmark/ActionCommand.kt
index a4345c43ac6a75667c3c3e85c8534697193e1458..9f0578f7d1456d823a29049daae6dbe886c95e2a 100644
--- a/theodolite/src/main/kotlin/theodolite/benchmark/ActionCommand.kt
+++ b/theodolite/src/main/kotlin/theodolite/benchmark/ActionCommand.kt
@@ -33,7 +33,7 @@ class ActionCommand(val client: NamespacedKubernetesClient) {
      * @return the exit code of this executed command
      */
     fun exec(
-        matchLabels: MutableMap<String, String>,
+        matchLabels: Map<String, String>,
         command: Array<String>,
         timeout: Long = Configuration.TIMEOUT_SECONDS,
         container: String = ""
@@ -58,7 +58,7 @@ class ActionCommand(val client: NamespacedKubernetesClient) {
 
             val latchTerminationStatus = execLatch.await(timeout, TimeUnit.SECONDS)
             if (!latchTerminationStatus) {
-                throw ActionCommandFailedException("Latch could not terminate within specified time")
+                throw ActionCommandFailedException("Timeout while running action command")
             }
             execWatch.close()
         } catch (e: Exception) {
@@ -112,7 +112,7 @@ class ActionCommand(val client: NamespacedKubernetesClient) {
      * it can take a while until the status is ready and the pod can be selected.
      * @return the name of the pod or throws [ActionCommandFailedException]
      */
-    fun getPodName(matchLabels: MutableMap<String, String>, tries: Int): String {
+    fun getPodName(matchLabels: Map<String, String>, tries: Int): String {
         for (i in 1..tries) {
 
             try {
@@ -125,7 +125,7 @@ class ActionCommand(val client: NamespacedKubernetesClient) {
         throw ActionCommandFailedException("Couldn't find any pod that matches the specified labels.")
     }
 
-    private fun getPodName(matchLabels: MutableMap<String, String>): String {
+    private fun getPodName(matchLabels: Map<String, String>): String {
         return try {
             val podNames = this.client
                 .pods()
diff --git a/theodolite/src/main/kotlin/theodolite/execution/operator/BenchmarkStateChecker.kt b/theodolite/src/main/kotlin/theodolite/execution/operator/BenchmarkStateChecker.kt
index 6dcfb582655ff9295aedd63d8c30cbac7daae2b3..c20b2ba87e386dc7c0a14245e03bedfb067720e6 100644
--- a/theodolite/src/main/kotlin/theodolite/execution/operator/BenchmarkStateChecker.kt
+++ b/theodolite/src/main/kotlin/theodolite/execution/operator/BenchmarkStateChecker.kt
@@ -190,7 +190,7 @@ class BenchmarkStateChecker(
     }
 }
 
-private fun <K, V> MutableMap<K, V>.containsMatchLabels(matchLabels: MutableMap<V, V>): Boolean {
+private fun <K, V> Map<K, V>.containsMatchLabels(matchLabels: Map<V, V>): Boolean {
     for (kv in matchLabels) {
         if (kv.value != this[kv.key as K]) {
             return false
diff --git a/theodolite/src/test/kotlin/theodolite/benchmark/ActionCommandTest.kt b/theodolite/src/test/kotlin/theodolite/benchmark/ActionCommandTest.kt
index 0e40fca5caf9fe721c547e09d2ba22c25860a1bf..47f0e52f45e46e3cda093ff1b9722071f22ef7e8 100644
--- a/theodolite/src/test/kotlin/theodolite/benchmark/ActionCommandTest.kt
+++ b/theodolite/src/test/kotlin/theodolite/benchmark/ActionCommandTest.kt
@@ -102,7 +102,7 @@ class ActionCommandTest {
         val action = Action()
         action.selector = ActionSelector()
         action.selector.pod = PodSelector()
-        action.selector.pod.matchLabels = mutableMapOf("app" to "pod")
+        action.selector.pod.matchLabels = mapOf("app" to "pod")
         action.exec = Command()
         action.exec.command = arrayOf("ls")
         action.exec.timeoutSeconds = 10L
@@ -118,7 +118,7 @@ class ActionCommandTest {
         val action = Action()
         action.selector = ActionSelector()
         action.selector.pod = PodSelector()
-        action.selector.pod.matchLabels = mutableMapOf("app" to "pod")
+        action.selector.pod.matchLabels = mapOf("app" to "pod")
         action.exec = Command()
         action.exec.command = arrayOf("error-command")
         action.exec.timeoutSeconds = 10L