diff --git a/commons/src/main/java/org/wikimedia/commons/Utils.java b/commons/src/main/java/org/wikimedia/commons/Utils.java
index f3bea5a54..49868d57d 100644
--- a/commons/src/main/java/org/wikimedia/commons/Utils.java
+++ b/commons/src/main/java/org/wikimedia/commons/Utils.java
@@ -38,7 +38,7 @@ public class Utils {
     public static String makeThumbBaseUrl(String filename) {
         String name = filename.replaceFirst("File:", "").replace(" ", "_");
         String sha = new String(Hex.encodeHex(DigestUtils.md5(name)));
-        return String.format("%s/%s/%s/%s", CommonsApplication.IMAGE_URL_BASE, sha.substring(0, 1), sha.substring(0, 2), name);
+        return String.format("%s/%s/%s/%s", CommonsApplication.IMAGE_URL_BASE, sha.substring(0, 1), sha.substring(0, 2), urlEncode(name));
     }