diff --git dom/system/OSFileConstants.cpp dom/system/OSFileConstants.cpp
index 4b21361..cb3be32 100644
--- dom/system/OSFileConstants.cpp
+++ dom/system/OSFileConstants.cpp
@@ -662,7 +662,7 @@
 
   { "OSFILE_SIZEOF_STATVFS", JS::Int32Value(sizeof (struct statvfs)) },
 
-  { "OSFILE_OFFSETOF_STATVFS_F_BSIZE", JS::Int32Value(offsetof (struct statvfs, f_bsize)) },
+  { "OSFILE_OFFSETOF_STATVFS_F_FRSIZE", JS::Int32Value(offsetof (struct statvfs, f_frsize)) },
   { "OSFILE_OFFSETOF_STATVFS_F_BAVAIL", JS::Int32Value(offsetof (struct statvfs, f_bavail)) },
 
 #endif // defined(XP_UNIX)
diff --git toolkit/components/osfile/modules/osfile_unix_back.jsm toolkit/components/osfile/modules/osfile_unix_back.jsm
index b59fca4..0cf220b 100644
--- toolkit/components/osfile/modules/osfile_unix_back.jsm
+++ toolkit/components/osfile/modules/osfile_unix_back.jsm
@@ -228,8 +228,8 @@
          let statvfs = new SharedAll.HollowStructure("statvfs",
            Const.OSFILE_SIZEOF_STATVFS);
 
-         statvfs.add_field_at(Const.OSFILE_OFFSETOF_STATVFS_F_BSIZE,
-                        "f_bsize", Type.unsigned_long.implementation);
+         statvfs.add_field_at(Const.OSFILE_OFFSETOF_STATVFS_F_FRSIZE,
+                        "f_frsize", Type.unsigned_long.implementation);
          statvfs.add_field_at(Const.OSFILE_OFFSETOF_STATVFS_F_BAVAIL,
                         "f_bavail", Type.fsblkcnt_t.implementation);
 
diff --git toolkit/components/osfile/modules/osfile_unix_front.jsm toolkit/components/osfile/modules/osfile_unix_front.jsm
index 99e5e9b..de642c5 100644
--- toolkit/components/osfile/modules/osfile_unix_front.jsm
+++ toolkit/components/osfile/modules/osfile_unix_front.jsm
@@ -373,7 +373,7 @@
        throw_on_negative("statvfs",  UnixFile.statvfs(sourcePath, fileSystemInfoPtr));
 
        let bytes = new Type.uint64_t.implementation(
-                        fileSystemInfo.f_bsize * fileSystemInfo.f_bavail);
+                        fileSystemInfo.f_frsize * fileSystemInfo.f_bavail);
 
        return bytes.value;
      };