diff --git a/src/compiler_llvm/compilation_unit.cc b/src/compiler_llvm/compilation_unit.cc
index b976fd2..66fdba0 100644
--- a/src/compiler_llvm/compilation_unit.cc
+++ b/src/compiler_llvm/compilation_unit.cc
@@ -57,6 +57,7 @@
 #include <llvm/Target/TargetData.h>
 #include <llvm/Target/TargetLibraryInfo.h>
 #include <llvm/Target/TargetMachine.h>
+#include <llvm/Transforms/IPO.h>
 #include <llvm/Transforms/IPO/PassManagerBuilder.h>
 
 #include <string>
@@ -222,7 +223,7 @@
 
   // Add optimization pass
   llvm::PassManagerBuilder pm_builder;
-  pm_builder.Inliner = NULL; // TODO: add some inline in the future
+  pm_builder.Inliner = llvm::createAlwaysInlinerPass();
   pm_builder.OptLevel = 1;
   pm_builder.DisableSimplifyLibCalls = 1;
   pm_builder.populateModulePassManager(pm);