diff -r e8959b23208b -r 5b8639cb0d11 src/Pure/Tools/scala_project.scala
--- a/src/Pure/Tools/scala_project.scala	Wed Feb 12 13:31:06 2025 +0100
+++ b/src/Pure/Tools/scala_project.scala	Wed Feb 12 13:32:04 2025 +0100
@@ -230,9 +230,8 @@
 
     progress.echo("Creating " + build_tool + " project directory: " + project_dir.absolute)
     Isabelle_System.make_directory(project_dir)
-
-    val java_src_dir = Isabelle_System.make_directory(project_dir + build_tool.java_src_dir)
-    val scala_src_dir = Isabelle_System.make_directory(project_dir + build_tool.scala_src_dir)
+    Isabelle_System.make_directory(project_dir + build_tool.java_src_dir)
+    Isabelle_System.make_directory(project_dir + build_tool.scala_src_dir)
 
     val (jars, sources) = isabelle_files
     isabelle_scala_files