diff --git a/build.gradle b/build.gradle
index 4ac25b2..c1f40d3 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,6 +1,6 @@
 plugins {
-    id 'org.jetbrains.kotlin.jvm' version '1.4.20'
-    id 'org.jetbrains.kotlin.plugin.serialization' version '1.4.20'
+    id 'org.jetbrains.kotlin.jvm' version '1.5.0'
+    id 'org.jetbrains.kotlin.plugin.serialization' version '1.5.0'
 }
 
 group 'intro-coroutines'
@@ -15,7 +15,7 @@ dependencies {
     implementation "org.jetbrains.kotlin:kotlin-reflect"
     implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.0.1")
 
-    def coroutines_version = '1.4.2'
+    def coroutines_version = '1.5.0'
     implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:$coroutines_version"
     implementation "org.jetbrains.kotlinx:kotlinx-coroutines-swing:$coroutines_version"
     implementation "org.jetbrains.kotlinx:kotlinx-coroutines-jdk8:$coroutines_version"
diff --git a/src/contributors/ContributorsUI.kt b/src/contributors/ContributorsUI.kt
index 8d73bcc..1077377 100644
--- a/src/contributors/ContributorsUI.kt
+++ b/src/contributors/ContributorsUI.kt
@@ -145,7 +145,7 @@ fun JPanel.addWideSeparator() {
 
 fun setDefaultFontSize(size: Float) {
     for (key in UIManager.getLookAndFeelDefaults().keys.toTypedArray()) {
-        if (key.toString().toLowerCase().contains("font")) {
+        if (key.toString().lowercase().contains("font")) {
             val font = UIManager.getDefaults().getFont(key) ?: continue
             val newFont = font.deriveFont(size)
             UIManager.put(key, newFont)
diff --git a/src/tasks/Aggregation.kt b/src/tasks/Aggregation.kt
index 145b344..8565e08 100644
--- a/src/tasks/Aggregation.kt
+++ b/src/tasks/Aggregation.kt
@@ -16,5 +16,5 @@ TODO: Write aggregation code.
 */
 fun List<User>.aggregate(): List<User> =
     groupBy { it.login }
-        .map { (login, group) -> User(login, group.sumBy { it.contributions }) }
+        .map { (login, group) -> User(login, group.sumOf { it.contributions }) }
         .sortedByDescending { it.contributions }
\ No newline at end of file
diff --git a/src/tasks/Request5NotCancellable.kt b/src/tasks/Request5NotCancellable.kt
index 87bac9a..efe549d 100644
--- a/src/tasks/Request5NotCancellable.kt
+++ b/src/tasks/Request5NotCancellable.kt
@@ -4,6 +4,7 @@ import contributors.*
 import kotlinx.coroutines.*
 import kotlin.coroutines.coroutineContext
 
+@OptIn(DelicateCoroutinesApi::class)
 suspend fun loadContributorsNotCancellable(service: GitHubService, req: RequestData): List<User> {
     val repos = service
         .getOrgRepos(req.org)