diff --git a/src/librustc/session/mod.rs b/src/librustc/session/mod.rs
index 43ed9f02157..f897ba4df1d 100644
--- a/src/librustc/session/mod.rs
+++ b/src/librustc/session/mod.rs
@@ -443,6 +443,9 @@ impl Session {
     pub fn nll_dump_cause(&self) -> bool {
         self.opts.debugging_opts.nll_dump_cause
     }
+    pub fn two_phase_borrows(&self) -> bool {
+        self.features.borrow().nll || self.opts.debugging_opts.two_phase_borrows
+    }
     pub fn emit_end_regions(&self) -> bool {
         self.opts.debugging_opts.emit_end_regions ||
             (self.opts.debugging_opts.mir_emit_validate > 0) ||
diff --git a/src/librustc_mir/borrow_check/mod.rs b/src/librustc_mir/borrow_check/mod.rs
index 34c91b84f28..b53e3e4c17a 100644
--- a/src/librustc_mir/borrow_check/mod.rs
+++ b/src/librustc_mir/borrow_check/mod.rs
@@ -774,7 +774,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
 
                 (Read(kind), BorrowKind::Unique) | (Read(kind), BorrowKind::Mut) => {
                     // Reading from mere reservations of mutable-borrows is OK.
-                    if this.tcx.sess.opts.debugging_opts.two_phase_borrows && index.is_reservation()
+                    if this.tcx.sess.two_phase_borrows() && index.is_reservation()
                     {
                         return Control::Continue;
                     }
@@ -922,7 +922,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                     BorrowKind::Shared => (Deep, Read(ReadKind::Borrow(bk))),
                     BorrowKind::Unique | BorrowKind::Mut => {
                         let wk = WriteKind::MutableBorrow(bk);
-                        if self.tcx.sess.opts.debugging_opts.two_phase_borrows {
+                        if self.tcx.sess.two_phase_borrows() {
                             (Deep, Reservation(wk))
                         } else {
                             (Deep, Write(wk))
@@ -1112,7 +1112,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         span: Span,
         flow_state: &Flows<'cx, 'gcx, 'tcx>,
     ) {
-        if !self.tcx.sess.opts.debugging_opts.two_phase_borrows {
+        if !self.tcx.sess.two_phase_borrows() {
             return;
         }
 
diff --git a/src/test/run-pass/borrowck/two-phase-control-flow-split-before-activation.rs b/src/test/run-pass/borrowck/two-phase-control-flow-split-before-activation.rs
index a891e6072a7..162314a8b79 100644
--- a/src/test/run-pass/borrowck/two-phase-control-flow-split-before-activation.rs
+++ b/src/test/run-pass/borrowck/two-phase-control-flow-split-before-activation.rs
@@ -10,7 +10,9 @@
 
 // revisions: lxl nll
 //[lxl]compile-flags: -Z borrowck=mir -Z two-phase-borrows
-//[nll]compile-flags: -Z borrowck=mir -Z two-phase-borrows -Z nll
+//[nll]compile-flags: -Z borrowck=mir
+
+#![cfg_attr(nll, feature(nll))]
 
 fn main() {
     let mut a = 0;