diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index a07891d846bc3319746c23f076b04de227f9ff58..d701926623daa2b1b7e6d6828c74c3f56b2c0e6c 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -14,13 +14,13 @@ cache:
     - .gradle/caches
 
 build:
-  image: openjdk:11
+  image: openjdk:8
   stage: build
   script:
     - ./gradlew assemble
 
 createDoc:
-  image: openjdk:11
+  image: openjdk:8
   stage: build
   script:
     - "./gradlew :run"
@@ -29,7 +29,7 @@ createDoc:
       - "pages/docs/config.md"
 
 publish:
-  image: openjdk:11
+  image: openjdk:8
   stage: publish
   script:
     - "./gradlew setDevVersionForCI"
diff --git a/build.gradle b/build.gradle
index 1ccfb713b7450908c5ec7c6954a0301b90420629..ac8b64524fa6219e8a76c76c7338ce1a7b364c0a 100644
--- a/build.gradle
+++ b/build.gradle
@@ -16,6 +16,8 @@ gradlePlugin {
     }
 }
 
+java.toolchain.languageVersion = JavaLanguageVersion.of(8)
+
 def versionFile = 'src/main/resources/PreprocessorTesting.properties'
 def oldProps = new Properties()