diff --git a/build.gradle.kts b/build.gradle.kts
index f67ed9728..64df29fce 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -18,7 +18,7 @@ dependencies {
 
 group = "net.sourceforge.plantuml"
 description = "PlantUML"
-java.sourceCompatibility = JavaVersion.VERSION_1_8
+java.sourceCompatibility = JavaVersion.VERSION_1_7
 
 java {
   withSourcesJar()