diff --git a/src/serialization/sb3.js b/src/serialization/sb3.js
index 816b1af19..3ffac8ead 100644
--- a/src/serialization/sb3.js
+++ b/src/serialization/sb3.js
@@ -75,7 +75,11 @@ const parseScratchObject = function (object, runtime) {
             rotationCenterX: costumeSource.rotationCenterX,
             rotationCenterY: costumeSource.rotationCenterY
         };
-        const costumeMd5 = `${costumeSource.assetId}.${costumeSource.dataFormat}`;
+        const dataFormat =
+            costumeSource.dataFormat ||
+            (costumeSource.assetType && costumeSource.assetType.runtimeFormat) || // older format
+            'png'; // if all else fails, guess that it might be a PNG
+        const costumeMd5 = `${costumeSource.assetId}.${dataFormat}`;
         return loadCostume(costumeMd5, costume, runtime);
     });
     // Sounds from JSON