diff --git a/build.xml b/build.xml
index 9228d17..5500678 100644
--- a/build.xml
+++ b/build.xml
@@ -660,6 +660,7 @@
       <arg value="--rerun-tasks"/>
       <arg value="--info"/>
       <arg value="--stacktrace"/>
+      <arg line="--warning-mode all" />
       <arg value="--no-daemon"/>
       <arg value="--gradle-user-home"/>
       <arg file="${gradle-test-user-dir}"/>
diff --git a/src/main/groovy/de/thetaphi/forbiddenapis/gradle/ForbiddenApisPlugin.groovy b/src/main/groovy/de/thetaphi/forbiddenapis/gradle/ForbiddenApisPlugin.groovy
index abc8185..875ea9d 100644
--- a/src/main/groovy/de/thetaphi/forbiddenapis/gradle/ForbiddenApisPlugin.groovy
+++ b/src/main/groovy/de/thetaphi/forbiddenapis/gradle/ForbiddenApisPlugin.groovy
@@ -47,8 +47,8 @@ public class ForbiddenApisPlugin extends ForbiddenApisPluginBase {
     }
 
     // Gradle is buggy with it's JavaVersion enum: We use majorVersion property before Java 11 (6,7,8,9,10) and for later we use toString() to be future-proof:
-    Closure targetCompatibilityGetter = { (project.targetCompatibility?.hasProperty('java11Compatible') && project.targetCompatibility?.java11Compatible) ?
-        project.targetCompatibility.toString() : project.targetCompatibility?.majorVersion };
+    Closure targetCompatibilityGetter = { (project.java.targetCompatibility?.hasProperty('java11Compatible') && project.java.targetCompatibility?.java11Compatible) ?
+        project.java.targetCompatibility.toString() : project.java.targetCompatibility?.majorVersion };
 
     // Define our tasks (one for each SourceSet):
     project.sourceSets.all{ sourceSet ->
diff --git a/src/test/gradle/build.gradle b/src/test/gradle/build.gradle
index 75e09bc..ab2b9a9 100644
--- a/src/test/gradle/build.gradle
+++ b/src/test/gradle/build.gradle
@@ -29,7 +29,9 @@ buildscript {
 apply plugin: 'java'
 apply plugin: 'de.thetaphi.forbiddenapis'
 
-sourceCompatibility = forbiddenSourceCompatibility
+java {
+  sourceCompatibility = forbiddenSourceCompatibility
+}
 
 sourceSets {
   main {