diff --git a/collects/teachpack/2htdp/batch-io.ss b/collects/teachpack/2htdp/batch-io.rkt
similarity index 100%
rename from collects/teachpack/2htdp/batch-io.ss
rename to collects/teachpack/2htdp/batch-io.rkt
diff --git a/collects/teachpack/2htdp/image.ss b/collects/teachpack/2htdp/image.rkt
similarity index 100%
rename from collects/teachpack/2htdp/image.ss
rename to collects/teachpack/2htdp/image.rkt
diff --git a/collects/teachpack/2htdp/universe.ss b/collects/teachpack/2htdp/universe.rkt
similarity index 100%
rename from collects/teachpack/2htdp/universe.ss
rename to collects/teachpack/2htdp/universe.rkt