diff --git a/grgit-core/build.gradle.kts b/grgit-core/build.gradle.kts
index 41957e30..6ba3eec1 100644
--- a/grgit-core/build.gradle.kts
+++ b/grgit-core/build.gradle.kts
@@ -4,9 +4,15 @@ plugins {
   id("org.gradle.test-retry")
 }
 
+java {
+  toolchain {
+    languageVersion.set(JavaLanguageVersion.of(11))
+  }
+}
+
 dependencies {
   // groovy
-  compileOnly("org.codehaus.groovy:groovy:[3.0, 4.0)")
+  api("org.codehaus.groovy:groovy:[3.0.9, 4.0)")
 
   // jgit
   api("org.eclipse.jgit:org.eclipse.jgit:[6.0, 7.0)")
@@ -18,6 +24,7 @@ testing {
       useSpock("2.0-groovy-3.0")
 
       dependencies {
+        implementation("org.codehaus.groovy:groovy:[3.0.9, 4.0)")
         implementation("org.junit.jupiter:junit-jupiter-api:latest.release")
 
         // logging
diff --git a/grgit-core/gradle.lockfile b/grgit-core/gradle.lockfile
index cce7b32c..2ecc3262 100644
--- a/grgit-core/gradle.lockfile
+++ b/grgit-core/gradle.lockfile
@@ -6,8 +6,7 @@ com.googlecode.javaewah:JavaEWAH:1.1.13=compileClasspath,runtimeClasspath,testCo
 net.bytebuddy:byte-buddy:1.11.0=testCompileClasspath,testRuntimeClasspath
 org.apiguardian:apiguardian-api:1.1.2=testCompileClasspath
 org.assertj:assertj-core:3.20.2=testCompileClasspath,testRuntimeClasspath
-org.codehaus.groovy:groovy:3.0.8=testCompileClasspath,testRuntimeClasspath
-org.codehaus.groovy:groovy:3.0.9=compileClasspath
+org.codehaus.groovy:groovy:3.0.9=compileClasspath,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
 org.eclipse.jgit:org.eclipse.jgit:6.0.0.202111291000-r=compileClasspath,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
 org.hamcrest:hamcrest:2.2=testCompileClasspath,testRuntimeClasspath
 org.jetbrains:annotations:20.1.0=testCompileClasspath,testRuntimeClasspath
diff --git a/grgit-gradle/build.gradle.kts b/grgit-gradle/build.gradle.kts
index 1c4de260..49769604 100644
--- a/grgit-gradle/build.gradle.kts
+++ b/grgit-gradle/build.gradle.kts
@@ -5,23 +5,16 @@ plugins {
   id("org.ajoberstar.stutter")
 }
 
-// avoid conflict with localGroovy()
-configurations.configureEach {
-  exclude(group = "org.codehaus.groovy")
-}
-
-// compat tests use grgit to set up and verify the tests
-sourceSets {
-  compatTest {
-    compileClasspath += sourceSets["main"].output
-    runtimeClasspath += sourceSets["main"].output
+java {
+  toolchain {
+    languageVersion.set(JavaLanguageVersion.of(11))
   }
 }
 
 dependencies {
-  compileOnly(gradleApi())
-
-  api(project(":grgit-core"))
+  api(project(":grgit-core")) {
+    exclude(group = "org.codehaus.groovy")
+  }
   compatTestImplementation(project(":grgit-core"))
 
   compatTestImplementation("org.spockframework:spock-core:2.0-groovy-3.0")
diff --git a/grgit-gradle/gradle.lockfile b/grgit-gradle/gradle.lockfile
index e1793757..e9fcc234 100644
--- a/grgit-gradle/gradle.lockfile
+++ b/grgit-gradle/gradle.lockfile
@@ -6,6 +6,7 @@ com.googlecode.javaewah:JavaEWAH:1.1.13=compatTestCompileClasspath,compatTestRun
 net.bytebuddy:byte-buddy:1.11.0=compatTestCompileClasspath,compatTestRuntimeClasspath
 org.apiguardian:apiguardian-api:1.1.0=compatTestCompileClasspath,compatTestRuntimeClasspath
 org.assertj:assertj-core:3.16.1=compatTestCompileClasspath,compatTestRuntimeClasspath
+org.codehaus.groovy:groovy:3.0.9=compatTestCompileClasspath,compatTestRuntimeClasspath
 org.eclipse.jgit:org.eclipse.jgit:6.0.0.202111291000-r=compatTestCompileClasspath,compatTestRuntimeClasspath,compileClasspath,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
 org.hamcrest:hamcrest:2.2=compatTestCompileClasspath,compatTestRuntimeClasspath
 org.jetbrains:annotations:20.1.0=compatTestCompileClasspath,compatTestRuntimeClasspath