diff --git a/Server-Protocol-Buffer/build.gradle b/Server-Protocol-Buffer/build.gradle
index 63f5ce8d7e13cc6dd26e61cd529737afa9c1d439..3a07b77dabe35c1e58c1b955ba770d0eb8e86c46 100644
--- a/Server-Protocol-Buffer/build.gradle
+++ b/Server-Protocol-Buffer/build.gradle
@@ -5,8 +5,8 @@ sourceSets {
     main.java.srcDirs += "${protobuf.generatedFilesBaseDir}/main/javalite"
 }
 
-sourceCompatibility = "8"
-targetCompatibility = "8"
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
 
 dependencies {
     implementation fileTree(dir: 'libs', include: ['*.jar'])