diff --git a/compiler/gen/src/llvm/build.rs b/compiler/gen/src/llvm/build.rs
index 4a5a8b0a64..773e3a1580 100644
--- a/compiler/gen/src/llvm/build.rs
+++ b/compiler/gen/src/llvm/build.rs
@@ -322,6 +322,7 @@ pub fn construct_optimization_passes<'a>(
             pmb.set_optimization_level(OptimizationLevel::None);
         }
         OptLevel::Optimize => {
+            pmb.set_optimization_level(OptimizationLevel::Aggressive);
             // this threshold seems to do what we want
             pmb.set_inliner_with_threshold(275);
 
@@ -1165,6 +1166,8 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
                         env.builder
                             .build_call(*function_value, &[], "evaluate_top_level_thunk");
 
+                    call.set_call_convention(FAST_CALL_CONV);
+
                     call.try_as_basic_value().left().unwrap()
                 }
                 None => {