diff --git a/gradle-plugin/build.gradle b/gradle-plugin/build.gradle
index 4946cfed..2ee21ed5 100644
--- a/gradle-plugin/build.gradle
+++ b/gradle-plugin/build.gradle
@@ -44,6 +44,11 @@ gradlePlugin {
   }
 }
 
+tasks.withType(JavaCompile) {
+    sourceCompatibility = JavaVersion.VERSION_1_8
+    targetCompatibility = JavaVersion.VERSION_1_8
+}
+
 publishing {
     publications.withType(MavenPublication) {
         pom {
diff --git a/maven-plugin/src/main/maven/plugin.xml b/maven-plugin/src/main/maven/plugin.xml
index 00f9767f..c0b98a3b 100644
--- a/maven-plugin/src/main/maven/plugin.xml
+++ b/maven-plugin/src/main/maven/plugin.xml
@@ -6,6 +6,10 @@
   <groupId>org.apache.pekko</groupId>
   <artifactId>pekko-grpc-maven-plugin</artifactId>
   <goalPrefix>pekko-grpc</goalPrefix>
+  <configuration>
+    <source>1.8</source>
+    <target>1.8</target>
+  </configuration>
   <mojos>
     <mojo>
       <goal>generate</goal>
diff --git a/project/Common.scala b/project/Common.scala
index ea80c511..02071be7 100644
--- a/project/Common.scala
+++ b/project/Common.scala
@@ -79,6 +79,13 @@ object Common extends AutoPlugin {
                                      "-Wconf:msg=unused import:silent",
                                      "-Wconf:cat=feature:silent")),
     Compile / console / scalacOptions ~= (_.filterNot(consoleDisabledOptions.contains)),
+    // restrict to 'compile' scope because otherwise it is also passed to
+    // javadoc and -target is not valid there.
+    // https://github.com/sbt/sbt/issues/1785
+    Compile / compile / javacOptions ++=
+      onlyAfterJdk8("--release", "8"),
+    Compile / compile / scalacOptions ++=
+      onlyAfterJdk8("-release", "8"),
     javacOptions ++= List("-Xlint:unchecked", "-Xlint:deprecation"),
     Compile / doc / scalacOptions := scalacOptions.value ++ Seq(
       "-doc-title",
@@ -110,6 +117,15 @@ object Common extends AutoPlugin {
     crossScalaVersions := Seq(scala212, scala213, scala3),
     mimaReportSignatureProblems := true)
 
+  val specificationVersion: String = sys.props("java.specification.version")
+
+  def isJdk8: Boolean =
+    VersionNumber(specificationVersion).matchesSemVer(SemanticSelector(s"=1.8"))
+
+  def onlyOnJdk8[T](values: T*): Seq[T] = if (isJdk8) values else Seq.empty[T]
+
+  def onlyAfterJdk8[T](values: T*): Seq[T] = if (isJdk8) Seq.empty[T] else values
+
   override lazy val buildSettings = Seq(
     dynverSonatypeSnapshots := true)
 }