diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 927b5479c33db..963df0fb4d70b 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -641,7 +641,10 @@ impl Session {
         self.opts.debugging_opts.binary_dep_depinfo
     }
     pub fn mir_opt_level(&self) -> usize {
-        self.opts.debugging_opts.mir_opt_level.unwrap_or(1)
+        self.opts
+            .debugging_opts
+            .mir_opt_level
+            .unwrap_or_else(|| if self.opts.optimize != config::OptLevel::No { 2 } else { 1 })
     }
 
     /// Gets the features enabled for the current compilation session.