diff --git a/collects/lang/htdp-langs.ss b/collects/lang/htdp-langs.ss
index 15e18c5194..d9b3317ec5 100644
--- a/collects/lang/htdp-langs.ss
+++ b/collects/lang/htdp-langs.ss
@@ -579,17 +579,20 @@
                               new-tps))))
                      settings)))
              (λ (settings name) 
-               (make-htdp-lang-settings
-                (drscheme:language:simple-settings-case-sensitive settings)
-                (drscheme:language:simple-settings-printing-style settings)
-                (drscheme:language:simple-settings-fraction-style settings)
-                (drscheme:language:simple-settings-show-sharing settings)
-                (drscheme:language:simple-settings-insert-newlines settings)
-                (drscheme:language:simple-settings-annotations settings)
-                (htdp-lang-settings-tracing? settings)
-                (filter (λ (x) (not (equal? (cadr x) name)))
-                        (htdp-lang-settings-teachpacks settings))))
+               (let ([new-tps (filter (λ (x) (not (equal? (cadr x) name)))
+                                      (htdp-lang-settings-teachpacks settings))])
+                 (preferences:set 'drscheme:htdp:last-set-teachpacks new-tps)
+                 (make-htdp-lang-settings
+                  (drscheme:language:simple-settings-case-sensitive settings)
+                  (drscheme:language:simple-settings-printing-style settings)
+                  (drscheme:language:simple-settings-fraction-style settings)
+                  (drscheme:language:simple-settings-show-sharing settings)
+                  (drscheme:language:simple-settings-insert-newlines settings)
+                  (drscheme:language:simple-settings-annotations settings)
+                  (htdp-lang-settings-tracing? settings)
+                  new-tps)))
              (λ (settings) 
+               (preferences:set 'drscheme:htdp:last-set-teachpacks '())
                (make-htdp-lang-settings
                 (drscheme:language:simple-settings-case-sensitive settings)
                 (drscheme:language:simple-settings-printing-style settings)