diff --git a/src/librustc_trans/back/lto.rs b/src/librustc_trans/back/lto.rs
index c88e76f42707..8a4059d1972a 100644
--- a/src/librustc_trans/back/lto.rs
+++ b/src/librustc_trans/back/lto.rs
@@ -167,7 +167,12 @@ pub fn run(sess: &session::Session, llmod: ModuleRef,
         llvm::LLVMRustAddAnalysisPasses(tm, pm, llmod);
         llvm::LLVMRustAddPass(pm, "verify\0".as_ptr() as *const _);
 
-        let opt = sess.opts.cg.opt_level.unwrap_or(0) as libc::c_uint;
+        let opt = match sess.opts.optimize {
+            config::No => 0,
+            config::Less => 1,
+            config::Default => 2,
+            config::Aggressive => 3,
+        };
 
         let builder = llvm::LLVMPassManagerBuilderCreate();
         llvm::LLVMPassManagerBuilderSetOptLevel(builder, opt);