diff --git a/checker/choices.go b/checker/choices.go
index 09d94678..8687610d 100644
--- a/checker/choices.go
+++ b/checker/choices.go
@@ -25,29 +25,73 @@ func treatWantChoices(pathname string, team *fic.Team) {
 
 	var ask wantChoices
 
-	if cnt_raw, err := ioutil.ReadFile(pathname); err != nil {
+	cnt_raw, err := ioutil.ReadFile(pathname)
+	if err != nil {
 		log.Printf("%s [ERR] %s\n", id, err)
-	} else if err = json.Unmarshal(cnt_raw, &ask); err != nil {
+		return
+	}
+
+	err = json.Unmarshal(cnt_raw, &ask)
+	if err != nil {
 		log.Printf("%s [ERR] %s\n", id, err)
-	} else if ask.FlagId == 0 {
+		return
+	}
+
+	if ask.FlagId == 0 {
 		log.Printf("%s [WRN] Invalid content in wantChoices file:  %s\n", id, pathname)
 		os.Remove(pathname)
-	} else if flag, err := fic.GetFlagKey(ask.FlagId); err != nil {
+		return
+	}
+
+	flag, err := fic.GetFlagKey(ask.FlagId)
+	if err != nil {
 		log.Printf("%s [ERR] %s\n", id, err)
-	} else if !team.CanSeeFlag(flag) {
+		return
+	}
+
+	if !team.CanSeeFlag(flag) {
 		log.Printf("%s [!!!] The team asks to display choices whereas it doesn't have access to the flag\n", id)
-	} else if exercice, err := flag.GetExercice(); err != nil {
+		return
+	}
+
+	exercice, err := flag.GetExercice()
+	if err != nil {
 		log.Printf("%s [ERR] Unable to retrieve the flag's underlying exercice: %s\n", id, err)
-	} else if !team.HasAccess(exercice) {
+		return
+	}
+
+	if !team.HasAccess(exercice) {
 		log.Printf("%s [!!!] The team asks to display choices whereas it doesn't have access to the exercice\n", id)
-	} else if exercice.Disabled {
+		return
+	}
+
+	if exercice.Disabled {
 		log.Println("[!!!] The team submits something for a disabled exercice")
-	} else if err = team.DisplayChoices(flag); err != nil {
-		log.Printf("%s [ERR] %s\n", id, err)
-	} else {
-		appendGenQueue(fic.GenStruct{Id: id, Type: fic.GenTeam, TeamId: team.Id})
-		if err = os.Remove(pathname); err != nil {
-			log.Printf("%s [ERR] %s\n", id, err)
+		return
+	}
+
+	if exercice.IdTheme != nil {
+		theme, err := fic.GetTheme(*exercice.IdTheme)
+		if err != nil {
+			log.Printf("%s [ERR] Unable to retrieve theme for exercice %d: %s\n", id, exercice.Id, err)
+			return
+		}
+
+		// Theme should not be locked
+		if theme.Locked {
+			log.Printf("%s [!!!] Want choice received for locked theme %d (fid=%d): %s\n", id, exercice.IdTheme, ask.FlagId, theme.Name)
+			return
 		}
 	}
+
+	err = team.DisplayChoices(flag)
+	if err != nil {
+		log.Printf("%s [ERR] %s\n", id, err)
+		return
+	}
+
+	appendGenQueue(fic.GenStruct{Id: id, Type: fic.GenTeam, TeamId: team.Id})
+	if err = os.Remove(pathname); err != nil {
+		log.Printf("%s [ERR] %s\n", id, err)
+	}
 }
diff --git a/checker/hint.go b/checker/hint.go
index f73d37f4..07d651b4 100644
--- a/checker/hint.go
+++ b/checker/hint.go
@@ -27,45 +27,88 @@ func treatOpeningHint(pathname string, team *fic.Team) {
 
 	var ask askOpenHint
 
-	if cnt_raw, err := ioutil.ReadFile(pathname); err != nil {
+	cnt_raw, err := ioutil.ReadFile(pathname)
+	if err != nil {
 		log.Printf("%s [ERR] %s\n", id, err)
-	} else if err = json.Unmarshal(cnt_raw, &ask); err != nil {
+		return
+	}
+
+	err = json.Unmarshal(cnt_raw, &ask)
+	if err != nil {
 		log.Printf("%s [ERR] %s\n", id, err)
-	} else if ask.HintId == 0 {
+		return
+	}
+
+	if ask.HintId == 0 {
 		log.Printf("%s [WRN] Invalid content in hint file: %s\n", id, pathname)
 		os.Remove(pathname)
-	} else if hint, err := fic.GetHint(ask.HintId); err != nil {
+		return
+	}
+
+	hint, err := fic.GetHint(ask.HintId)
+	if err != nil {
 		log.Printf("%s [ERR] Unable to retrieve the given hint: %s\n", id, err)
-	} else if exercice, err := hint.GetExercice(); err != nil {
+		return
+	}
+
+	exercice, err := hint.GetExercice()
+	if err != nil {
 		log.Printf("%s [ERR] Unable to retrieve the hint's underlying exercice: %s\n", id, err)
-	} else if exercice.Disabled {
+		return
+	}
+
+	if exercice.Disabled {
 		log.Println("[!!!] The team submits something for a disabled exercice")
-	} else if !team.HasAccess(exercice) {
+		return
+	}
+
+	if !team.HasAccess(exercice) {
 		log.Printf("%s [!!!] The team asks to open an hint whereas it doesn't have access to the exercice\n", id)
-	} else if !team.CanSeeHint(hint) {
+		return
+	}
+
+	if !team.CanSeeHint(hint) {
 		log.Printf("%s [!!!] The team asks to open an hint whereas it doesn't have access to it due to hint dependencies\n", id)
-	} else if err = team.OpenHint(hint); err != nil && !fic.DBIsDuplicateKeyError(err) { // Skip DUPLICATE KEY errors
-		log.Printf("%s [ERR] Unable to open hint: %s\n", id, err)
-	} else {
-		if exercice.IdTheme == nil {
-			if _, err = fic.NewEvent(fmt.Sprintf("L'équipe %s a dévoilé un indice pour le défi %s !", html.EscapeString(team.Name), exercice.Title), "info"); err != nil {
-				log.Printf("%s [WRN] Unable to create event: %s\n", id, err)
-			}
-		} else {
-			// Write event
-			if lvl, err := exercice.GetLevel(); err != nil {
-				log.Printf("%s [WRN] %s\n", id, err)
-			} else if theme, err := fic.GetTheme(*exercice.IdTheme); err != nil {
-				log.Printf("%s [WRN] %s\n", id, err)
-			} else if _, err = fic.NewEvent(fmt.Sprintf("L'équipe %s a dévoilé un indice pour le <strong>%d<sup>e</sup></strong> défi %s&#160;!", html.EscapeString(team.Name), lvl, theme.Name), "info"); err != nil {
-				log.Printf("%s [WRN] Unable to create event: %s\n", id, err)
-			}
+		return
+	}
+
+	// Find the corresponding theme
+	var theme *fic.Theme
+	if exercice.IdTheme != nil {
+		theme, err = fic.GetTheme(*exercice.IdTheme)
+		if err != nil {
+			log.Printf("%s [ERR] Unable to retrieve theme for exercice %d: %s\n", id, exercice.Id, err)
+			return
 		}
 
-		appendGenQueue(fic.GenStruct{Id: id, Type: fic.GenTeam, TeamId: team.Id})
-		appendGenQueue(fic.GenStruct{Id: id, Type: fic.GenEvents})
-		if err = os.Remove(pathname); err != nil {
-			log.Printf("%s [ERR] %s\n", id, err)
+		// Theme should not be locked
+		if theme.Locked {
+			log.Printf("%s [!!!] Open hint received for locked theme %d (hid=%d): %s\n", id, exercice.IdTheme, ask.HintId, theme.Name)
+			return
 		}
 	}
+
+	if err = team.OpenHint(hint); err != nil && !fic.DBIsDuplicateKeyError(err) { // Skip DUPLICATE KEY errors
+		log.Printf("%s [ERR] Unable to open hint: %s\n", id, err)
+		return
+	}
+
+	if theme == nil {
+		if _, err = fic.NewEvent(fmt.Sprintf("L'équipe %s a dévoilé un indice pour le défi %s&#160;!", html.EscapeString(team.Name), exercice.Title), "info"); err != nil {
+			log.Printf("%s [WRN] Unable to create event: %s\n", id, err)
+		}
+	} else {
+		// Write event
+		if lvl, err := exercice.GetLevel(); err != nil {
+			log.Printf("%s [WRN] %s\n", id, err)
+		} else if _, err = fic.NewEvent(fmt.Sprintf("L'équipe %s a dévoilé un indice pour le <strong>%d<sup>e</sup></strong> défi %s&#160;!", html.EscapeString(team.Name), lvl, theme.Name), "info"); err != nil {
+			log.Printf("%s [WRN] Unable to create event: %s\n", id, err)
+		}
+	}
+
+	appendGenQueue(fic.GenStruct{Id: id, Type: fic.GenTeam, TeamId: team.Id})
+	appendGenQueue(fic.GenStruct{Id: id, Type: fic.GenEvents})
+	if err = os.Remove(pathname); err != nil {
+		log.Printf("%s [ERR] %s\n", id, err)
+	}
 }