--- a/xpcom/io/CocoaFileUtils.mm
+++ b/xpcom/io/CocoaFileUtils.mm
@@ -234,21 +234,21 @@ void AddQuarantineMetadataToFile(const C
 
   // Add metadata that the OS couldn't infer.
 
   if (!::CFDictionaryGetValue(mutQuarantineProps, kLSQuarantineTypeKey)) {
     CFStringRef type = isFromWeb ? kLSQuarantineTypeWebDownload : kLSQuarantineTypeOtherDownload;
     ::CFDictionarySetValue(mutQuarantineProps, kLSQuarantineTypeKey, type);
   }
 
-  if (!::CFDictionaryGetValue(mutQuarantineProps, kLSQuarantineOriginURLKey)) {
+  if (!::CFDictionaryGetValue(mutQuarantineProps, kLSQuarantineOriginURLKey) && referrerURL) {
     ::CFDictionarySetValue(mutQuarantineProps, kLSQuarantineOriginURLKey, referrerURL);
   }
 
-  if (!::CFDictionaryGetValue(mutQuarantineProps, kLSQuarantineDataURLKey)) {
+  if (!::CFDictionaryGetValue(mutQuarantineProps, kLSQuarantineDataURLKey) && sourceURL) {
     ::CFDictionarySetValue(mutQuarantineProps, kLSQuarantineDataURLKey, sourceURL);
   }
 
   // Set quarantine properties on file.
   ::CFURLSetResourcePropertyForKey(fileURL,
                                    quarantinePropKey,
                                    mutQuarantineProps,
                                    NULL);