diff --git a/src/scratch/ScratchObj.as b/src/scratch/ScratchObj.as
index 3e99861..721c069 100644
--- a/src/scratch/ScratchObj.as
+++ b/src/scratch/ScratchObj.as
@@ -132,22 +132,6 @@ public class ScratchObj extends Sprite {
 		return currentCostumeIndex + 1;
 	}
 
-	public function isCostumeNameUsed(name:String):Boolean {
-		name = name.toLowerCase();
-		for each (var c:ScratchCostume in costumes) {
-			if (c.costumeName.toLowerCase() == name) return true;
-		}
-		return false;
-	}
-
-	public function isSoundNameUsed(name:String):Boolean {
-		name = name.toLowerCase();
-		for each (var s:ScratchSound in sounds) {
-			if (s.soundName.toLowerCase() == name) return true;
-		}
-		return false;
-	}
-
 	public function unusedCostumeName(baseName:String = ''):String {
 		// Create a unique costume name by appending a number if necessary.
 		if (baseName == '') baseName = Translator.map(isStage ? 'backdrop1' : 'costume1');
diff --git a/src/scratch/ScratchRuntime.as b/src/scratch/ScratchRuntime.as
index abd4231..e34b9c5 100644
--- a/src/scratch/ScratchRuntime.as
+++ b/src/scratch/ScratchRuntime.as
@@ -676,7 +676,7 @@ public class ScratchRuntime {
 		var obj:ScratchObj = app.viewedObj();
 		var costume:ScratchCostume = obj.currentCostume();
 		var oldName:String = costume.costumeName;
-		if (obj.isCostumeNameUsed(newName)) return;
+		newName = obj.unusedCostumeName(newName || 'costume1');
 		costume.costumeName = newName;
 		updateArgs(obj.isStage ? allUsesOfBackdrop(oldName) : allUsesOfCostume(oldName), newName);
 	}
@@ -703,7 +703,7 @@ public class ScratchRuntime {
     public function renameSound(s:ScratchSound, newName:String):void {
         var obj:ScratchObj = app.viewedObj();
         var oldName:String = s.soundName;
-        if (obj.isSoundNameUsed(newName)) return;
+        newName = obj.unusedSoundName(newName || 'sound1');
         s.soundName = newName;
         allUsesOfSoundDo(oldName, function (a:BlockArg):void {
             a.setArgValue(newName);