diff --git a/modules/libjar/nsZipArchive.cpp b/modules/libjar/nsZipArchive.cpp
index 764d40914fa9..9ab949c89561 100644
--- a/modules/libjar/nsZipArchive.cpp
+++ b/modules/libjar/nsZipArchive.cpp
@@ -715,7 +715,7 @@ nsresult nsZipArchive::BuildFileList(PRFileDesc* aFd)
     sig = 0;
   } /* while reading central directory records */
 
-  if (sig != ENDSIG) {
+  if (sig != ENDSIG && sig != ENDSIG64) {
     return NS_ERROR_FILE_CORRUPTED;
   }
 
diff --git a/modules/libjar/zipstruct.h b/modules/libjar/zipstruct.h
index f4739cc1087f..2770634c5ad2 100644
--- a/modules/libjar/zipstruct.h
+++ b/modules/libjar/zipstruct.h
@@ -83,6 +83,7 @@ typedef struct ZipEnd_ {
 #define LOCALSIG 0x04034B50l
 #define CENTRALSIG 0x02014B50l
 #define ENDSIG 0x06054B50l
+#define ENDSIG64 0x6064B50l
 
 /* extra fields */
 #define EXTENDED_TIMESTAMP_FIELD 0x5455