diff --git a/mirai-japt/build.gradle.kts b/mirai-japt/build.gradle.kts
index 4b592fd06..1c4be4095 100644
--- a/mirai-japt/build.gradle.kts
+++ b/mirai-japt/build.gradle.kts
@@ -39,6 +39,11 @@ description = "Java helper for Mirai"
 val mirai_japt_version: String by rootProject.ext
 version = mirai_japt_version
 
+java {
+    sourceCompatibility = JavaVersion.VERSION_1_8
+    targetCompatibility = JavaVersion.VERSION_1_8
+}
+
 kotlin {
     sourceSets {
         all {