diff --git a/README.md b/README.md
index 384c486..ea2fb9d 100644
--- a/README.md
+++ b/README.md
@@ -121,7 +121,8 @@
 To build `freemarker.jar`, just issue `./gradlew jar` in the project root directory,
 and it should download all dependencies automatically and build `freemarker.jar`.
 
-To run all checks, issue `./gradlew check`.
+To run all JUnit tests and some other checks, issue `./gradlew check`. (Avoid the
+`test` task, as that will only run the tests of the `core` source set.)
 
 To generate documentation, issue `./gradlew javadoc` and `./gradlew manualOffline`.
 
diff --git a/build.gradle.kts b/build.gradle.kts
index 84f2c3b..114ac08 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -52,6 +52,10 @@
 }
 
 freemarkerRoot {
+    // FreeMarker 2.x build is unusual in that instead of using a nested Gradle project for each logical module,
+    // it uses a source set for each. This is because FreeMarker 2.x is a single monolithic artifact for historical
+    // reasons.
+
     configureSourceSet(SourceSet.MAIN_SOURCE_SET_NAME) { enableTests() }
     configureSourceSet("javaxServlet") { enableTests() }
     configureSourceSet("jython20")
diff --git a/buildSrc/src/main/kotlin/freemarker/build/FreemarkerRootExtension.kt b/buildSrc/src/main/kotlin/freemarker/build/FreemarkerRootExtension.kt
index ddef3a3..ff23f7a 100644
--- a/buildSrc/src/main/kotlin/freemarker/build/FreemarkerRootExtension.kt
+++ b/buildSrc/src/main/kotlin/freemarker/build/FreemarkerRootExtension.kt
@@ -97,11 +97,10 @@
     val compilerVersion: JavaLanguageVersion
 ) {
     val main = sourceSetName == SourceSet.MAIN_SOURCE_SET_NAME
-    val baseDirName = if (main) "core" else sourceSetName.camelCaseToDashed()
 
     val sourceSet = context.sourceSets.maybeCreate(sourceSetName)
 
-    val sourceSetRootDirName = "freemarker-${baseDirName}"
+    val sourceSetRootDirName = "freemarker-${if (main) "core" else sourceSetName.camelCaseToDashed()}"
     val sourceSetSrcPath = sourceSetRoot(context, generated, sourceSetRootDirName)
 
     fun generateJakartaSources(