diff --git a/admin/sync/exercices.go b/admin/sync/exercices.go
index 049abb73..f06c8517 100644
--- a/admin/sync/exercices.go
+++ b/admin/sync/exercices.go
@@ -106,7 +106,7 @@ func SyncExercices(i Importer, theme fic.Theme) []string {
 							for k, _ := range dmap {
 								dmap_keys = append(dmap_keys, fmt.Sprintf("%d", k))
 							}
-							errs = append(errs, fmt.Sprintf("%q: Unable to find required dependancy %q (available at time of processing: %s)", edir, p.Dependencies[0].Id, strings.Join(dmap_keys, ",")))
+							errs = append(errs, fmt.Sprintf("%q: Unable to find required dependancy %d (available at time of processing: %s)", edir, p.Dependencies[0].Id, strings.Join(dmap_keys, ",")))
 						}
 					}
 				}
@@ -162,7 +162,7 @@ func SyncExercices(i Importer, theme fic.Theme) []string {
 		if exercices, err := theme.GetExercices(); err == nil {
 			for _, ex := range exercices {
 				if _, ok := emap[ex.Title]; !ok {
-					ex.Delete()
+					ex.DeleteCascade()
 				}
 			}
 		}
diff --git a/libfic/exercice.go b/libfic/exercice.go
index fcafada7..cb71ffcd 100644
--- a/libfic/exercice.go
+++ b/libfic/exercice.go
@@ -190,6 +190,52 @@ func (e Exercice) Delete() (int64, error) {
 	}
 }
 
+// DeleteCascade the challenge from the database, including inner content but not player content.
+func (e Exercice) DeleteCascade() (int64, error) {
+	if _, err := DBExec("UPDATE exercices SET id_depend = NULL WHERE id_depend = ?", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM exercice_files_deps WHERE id_file IN (SELECT id_file FROM exercice_files WHERE id_exercice = ?)", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM exercice_files WHERE id_exercice = ?", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM exercice_hints WHERE id_exercice = ?", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM exercice_flags_deps WHERE id_flag IN (SELECT id_flag FROM exercice_flags WHERE id_exercice = ?)", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM exercice_flags_choices WHERE id_flag IN (SELECT id_flag FROM exercice_flags WHERE id_exercice = ?)", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM exercice_flags WHERE id_exercice = ?", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM mcq_entries WHERE id_mcq IN (SELECT id_mcq FROM exercice_flags WHERE id_exercice = ?)", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM exercice_mcq WHERE id_exercice = ?", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM exercice_tags WHERE id_exercice = ?", e.Id); err != nil {
+		return 0, err
+	} else {
+		return e.Delete()
+	}
+}
+
+// DeleteDeep the challenge from the database, including player content.
+func (e Exercice) DeleteDeep() (int64, error) {
+	if _, err := DBExec("DELETE FROM mcq_found WHERE id_mcq IN (SELECT id_mcq FROM exercice_mcq WHERE id_exercice = ?)", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM flag_found WHERE id_flag IN (SELECT id_flag FROM exercice_flags WHERE id_exercice = ?)", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM team_hints WHERE id_hint IN (SELECT id_hint FROM exercice_hints WHERE id_exercice = ?)", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM team_wchoices WHERE id_flag IN (SELECT id_flag FROM exercice_flags WHERE id_exercice = ?)", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM exercice_solved WHERE id_exercice = ?", e.Id); err != nil {
+		return 0, err
+	} else if _, err := DBExec("DELETE FROM exercice_tries WHERE id_exercice = ?", e.Id); err != nil {
+		return 0, err
+	} else {
+		return e.DeleteCascade()
+	}
+}
+
 // GetLevel returns the number of dependancy challenges.
 func (e Exercice) GetLevel() (int, error) {
 	dep := e.Depend