diff --git a/toolkit/mozapps/downloads/DownloadUtils.jsm b/toolkit/mozapps/downloads/DownloadUtils.jsm
index df74b4605f..60fc6e0285 100644
--- a/toolkit/mozapps/downloads/DownloadUtils.jsm
+++ b/toolkit/mozapps/downloads/DownloadUtils.jsm
@@ -497,14 +497,16 @@ this.DownloadUtils = {
     // Don't try to format Infinity values using NumberFormat.
     if (aBytes === Infinity) {
       aBytes = "Infinity";
-    } else if (typeof Intl != "undefined") {
-      aBytes = getLocaleNumberFormat(fractionDigits)
-                 .format(aBytes);
     } else {
-      // FIXME: Fall back to the old hack, will be fixed in bug 1200494.
-      aBytes = aBytes.toFixed(fractionDigits);
-      if (gDecimalSymbol != ".") {
-        aBytes = aBytes.replace(".", gDecimalSymbol);
+      try {
+        aBytes = getLocaleNumberFormat(fractionDigits)
+                   .format(aBytes);
+      } catch(e) {
+        // FIXME: Fall back to the old hack, will be fixed in bug 1200494.
+        aBytes = aBytes.toFixed(fractionDigits);
+        if (gDecimalSymbol != ".") {
+          aBytes = aBytes.replace(".", gDecimalSymbol);
+        }
       }
     }