diff --git a/build.gradle.kts b/build.gradle.kts
index 3f514ac91..c7995514a 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -35,6 +35,15 @@ group = "org.freemarker"
 
 val fmExt = freemarkerRoot
 
+
+val core9JavaVersion = providers
+        .gradleProperty("freemarker.core9.javaVersion")
+        .get()
+
+val core16JavaVersion = providers
+        .gradleProperty("freemarker.core16.javaVersion")
+        .get()
+
 tasks.withType<JavaCompile>().configureEach {
     options.encoding = "UTF-8"
 }
@@ -61,8 +70,8 @@ freemarkerRoot {
     configureSourceSet("jython20")
     configureSourceSet("jython22")
     configureSourceSet("jython25") { enableTests() }
-    configureSourceSet("core9", "9") { enableTests() }
-    configureSourceSet("core16", "16") {
+    configureSourceSet("core9", core9JavaVersion) { enableTests() }
+    configureSourceSet("core16", core16JavaVersion) {
         enableTests();
         addDependencySourceSet("core9");
     }
diff --git a/gradle.properties b/gradle.properties
index 46ce0468c..1a4847465 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -21,10 +21,14 @@
 
 # JDK version used for compiling, except for Source Sets where a specific version is set in build.gradle.kts.
 freemarker.javaVersion=8
+# JDK version used for compiling the Java 9 MR-JAR source set
+freemarker.core9.javaVersion=11
+# JDK version used for compiling the Java 16 MR-JAR source set
+freemarker.core16.javaVersion=17
 # JDK version for running javadoc
-freemarker.javadoc.javaVersion=16
+freemarker.javadoc.javaVersion=17
 # JDK version for running JUnit tests
-freemarker.test.javaVersion=16
+freemarker.test.javaVersion=17
 
 # Method used when generating the *.asc file, one of: none, gradle_properties, gpg_command
 freemarker.signMethod=none