diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index 60d5340613c2..836f42ff4ba7 100644
--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -1216,8 +1216,6 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "make unnamed regions display as '# (where # is some non-ident unique id)"),
     borrowck: Option<String> = (None, parse_opt_string, [UNTRACKED],
         "select which borrowck is used (`ast`, `mir`, `migrate`, or `compare`)"),
-    two_phase_borrows: bool = (false, parse_bool, [UNTRACKED],
-        "use two-phase reserved/active distinction for `&mut` borrows in MIR borrowck"),
     two_phase_beyond_autoref: bool = (false, parse_bool, [UNTRACKED],
         "when using two-phase-borrows, allow two phases even for non-autoref `&mut` borrows"),
     time_passes: bool = (false, parse_bool, [UNTRACKED],