diff --git a/nac3artiq/src/lib.rs b/nac3artiq/src/lib.rs
index 80f8222..3c05d72 100644
--- a/nac3artiq/src/lib.rs
+++ b/nac3artiq/src/lib.rs
@@ -8,7 +8,7 @@ use std::sync::Arc;
 use inkwell::{
     memory_buffer::MemoryBuffer,
     module::{Linkage, Module},
-    passes::PassBuilderOptions,
+    passes::{PassManager, PassManagerBuilder},
     targets::*,
     OptimizationLevel,
 };
@@ -654,16 +654,12 @@ impl Nac3 {
             global_option = global.get_next_global();
         }
 
-        let target_machine = self.llvm_options.target
-            .create_target_machine(self.llvm_options.opt_level)
-            .expect("couldn't create target machine");
-
-        let pass_options = PassBuilderOptions::create();
-        pass_options.set_merge_functions(true);
-        let result = main.run_passes("default<O3>", &target_machine, pass_options);
-        if let Err(err) = result {
-            panic!("Failed to run optimization for module `main`: {}", err.to_string());
-        }
+        let builder = PassManagerBuilder::create();
+        builder.set_optimization_level(OptimizationLevel::Aggressive);
+        let passes = PassManager::create(());
+        builder.set_inliner_with_threshold(255);
+        builder.populate_module_pass_manager(&passes);
+        passes.run_on(&main);
 
         link_fn(&main)
     }
diff --git a/nac3core/src/codegen/mod.rs b/nac3core/src/codegen/mod.rs
index 0d8e3c8..c741aa6 100644
--- a/nac3core/src/codegen/mod.rs
+++ b/nac3core/src/codegen/mod.rs
@@ -15,7 +15,7 @@ use inkwell::{
     builder::Builder,
     context::Context,
     module::Module,
-    passes::PassBuilderOptions,
+    passes::{PassManager, PassManagerBuilder},
     targets::{CodeModel, RelocMode, Target, TargetMachine, TargetTriple},
     types::{AnyType, BasicType, BasicTypeEnum},
     values::{BasicValueEnum, FunctionValue, PhiValue, PointerValue},
@@ -32,6 +32,7 @@ use std::sync::{
     Arc,
 };
 use std::thread;
+use lazy_static::lazy_static;
 
 pub mod concrete_type;
 pub mod expr;
@@ -53,6 +54,12 @@ pub struct StaticValueStore {
 
 pub type VarValue<'ctx> = (PointerValue<'ctx>, Option<Arc<dyn StaticValue + Send + Sync>>, i64);
 
+lazy_static!(
+    // HACK: The Mutex is a work-around for issue
+    // https://git.m-labs.hk/M-Labs/nac3/issues/275
+    static ref PASSES_INIT_LOCK: Mutex<AtomicBool> = Mutex::new(AtomicBool::new(true));
+);
+
 /// Additional options for LLVM during codegen.
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct CodeGenLLVMOptions {
@@ -298,11 +305,23 @@ impl WorkerRegistry {
             context.i32_type().const_int(4, false),
         );
 
+        let passes = PassManager::create(&module);
+
+        // HACK: This critical section is a work-around for issue
+        // https://git.m-labs.hk/M-Labs/nac3/issues/275
+        {
+            let _data = PASSES_INIT_LOCK.lock();
+            let pass_builder = PassManagerBuilder::create();
+            pass_builder.set_optimization_level(self.llvm_options.opt_level);
+            pass_builder.populate_function_pass_manager(&passes);
+        }
+
         let mut errors = HashSet::new();
         while let Some(task) = self.receiver.recv().unwrap() {
             match gen_func(&context, generator, self, builder, module, task) {
                 Ok(result) => {
                     builder = result.0;
+                    passes.run_on(&result.2);
                     module = result.1;
                 }
                 Err((old_builder, e)) => {
@@ -326,21 +345,9 @@ impl WorkerRegistry {
             panic!()
         }
 
-        let pass_options = PassBuilderOptions::create();
-        let target_machine = self.llvm_options.target.create_target_machine(
-            self.llvm_options.opt_level
-        ).expect(format!("could not create target machine from properties {:?}", self.llvm_options.target).as_str());
-        let passes = format!("default<O{}>", self.llvm_options.opt_level as u32);
-
-        let result = module.run_passes(passes.as_str(), &target_machine, pass_options);
-        if let Err(err) = result {
-            panic!("Failed to run optimization for module `{}`: {}",
-                   module.get_name().to_str().unwrap(),
-                   err.to_string());
-        }
-
         if self.llvm_options.emit_llvm {
-            println!("LLVM IR for {}\n{}", module.get_name().to_str().unwrap(), module.to_string());
+            println!("LLVM IR for {}", module.get_name().to_str().unwrap());
+            println!("{}", module.to_string());
             println!();
         }
 
diff --git a/nac3standalone/src/main.rs b/nac3standalone/src/main.rs
index f1a2160..732fca1 100644
--- a/nac3standalone/src/main.rs
+++ b/nac3standalone/src/main.rs
@@ -1,7 +1,7 @@
 use clap::Parser;
 use inkwell::{
     memory_buffer::MemoryBuffer,
-    passes::PassBuilderOptions,
+    passes::{PassManager, PassManagerBuilder},
     targets::*,
     OptimizationLevel,
 };
@@ -357,17 +357,16 @@ fn main() {
         function_iter = func.get_next_function();
     }
 
+    let builder = PassManagerBuilder::create();
+    builder.set_optimization_level(OptimizationLevel::Aggressive);
+    let passes = PassManager::create(());
+    builder.set_inliner_with_threshold(255);
+    builder.populate_module_pass_manager(&passes);
+    passes.run_on(&main);
+
     let target_machine = llvm_options.target
         .create_target_machine(llvm_options.opt_level)
         .expect("couldn't create target machine");
-
-    let pass_options = PassBuilderOptions::create();
-    pass_options.set_merge_functions(true);
-    let result = main.run_passes("default<O3>", &target_machine, pass_options);
-    if let Err(err) = result {
-        panic!("Failed to run optimization for module `main`: {}", err.to_string());
-    }
-
     target_machine
         .write_to_file(&main, FileType::Object, Path::new("module.o"))
         .expect("couldn't write module to file");