diff --git a/src/librustc/session/mod.rs b/src/librustc/session/mod.rs
index 37bdd1673e9ca..c120ac53b7811 100644
--- a/src/librustc/session/mod.rs
+++ b/src/librustc/session/mod.rs
@@ -202,6 +202,9 @@ impl Session {
     pub fn show_span(&self) -> bool {
         self.debugging_opt(config::SHOW_SPAN)
     }
+    pub fn unstable_options(&self) -> bool {
+        self.debugging_opt(config::UNSTABLE_OPTIONS)
+    }
     pub fn sysroot<'a>(&'a self) -> &'a Path {
         match self.opts.maybe_sysroot {
             Some (ref sysroot) => sysroot,
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index e2791aff14e49..5cd87a1e4c080 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -143,7 +143,7 @@ fn run_compiler(args: &[String]) {
         pretty::parse_pretty(&sess, a.as_slice(), false)
     });
     let pretty = if pretty.is_none() &&
-        sess.debugging_opt(config::UNSTABLE_OPTIONS) {
+        sess.unstable_options() {
             matches.opt_str("xpretty").map(|a| {
                 // extended with unstable pretty-print variants
                 pretty::parse_pretty(&sess, a.as_slice(), true)