diff --git a/modules/libjar/nsZipArchive.cpp b/modules/libjar/nsZipArchive.cpp
index 1ee3839baa..e5cf18d9e6 100644
--- a/modules/libjar/nsZipArchive.cpp
+++ b/modules/libjar/nsZipArchive.cpp
@@ -310,6 +310,8 @@ MOZ_WIN_MEM_TRY_BEGIN
       mFileData = mFileStart + headerSize;
       return NS_OK;
     }
+    // If we get here, the file was truncated.
+    return NS_ERROR_FILE_CORRUPTED;
   }
   mLen = mTotalLen;
   mFileData = mFileStart;