diff --git a/server/build.gradle.kts b/server/build.gradle.kts
index a6fb4b3..06b6e69 100644
--- a/server/build.gradle.kts
+++ b/server/build.gradle.kts
@@ -14,11 +14,13 @@ application {
 }
 
 kotlin {
-    compilerOptions {
-        optIn = listOf(
-            "kotlinx.coroutines.DelicateCoroutinesApi",
-            "kotlinx.serialization.ExperimentalSerializationApi",
-        )
+    sourceSets {
+        main {
+            languageSettings.apply {
+                optIn("kotlinx.coroutines.DelicateCoroutinesApi")
+                optIn("kotlinx.serialization.ExperimentalSerializationApi")
+            }
+        }
     }
 }
 
diff --git a/shared/build.gradle.kts b/shared/build.gradle.kts
index 5be9fb0..402f3e6 100644
--- a/shared/build.gradle.kts
+++ b/shared/build.gradle.kts
@@ -30,6 +30,11 @@ kotlin {
     jvm()
 
     sourceSets {
+        all {
+            languageSettings.apply {
+                optIn("kotlinx.serialization.ExperimentalSerializationApi")
+            }
+        }
         commonMain.dependencies {
             implementation(libs.ktor.serialization.kotlinx.cbor)
             implementation(libs.ktor.shared.resources)