--- a/src/libasr/codegen/KaleidoscopeJIT.h
+++ b/src/libasr/codegen/KaleidoscopeJIT.h
@@ -25,6 +25,7 @@
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/LLVMContext.h"
 #include <memory>
+#include <optional>
 
 namespace llvm {
 namespace orc {
@@ -71,7 +72,7 @@
     auto CPU = "generic";
     auto Features = "";
     TargetOptions opt;
-    auto RM = Optional<Reloc::Model>();
+    auto RM = std::optional<Reloc::Model>();
     TM = Target->createTargetMachine(TargetTriple, CPU, Features, opt, RM);
   }
 
--- a/src/libasr/codegen/asr_to_llvm.cpp
+++ b/src/libasr/codegen/asr_to_llvm.cpp
@@ -276,7 +276,7 @@
             // to our new block
             builder->CreateBr(bb);
         }
-        fn->getBasicBlockList().push_back(bb);
+        fn->insert(fn->end(), bb);
         builder->SetInsertPoint(bb);
     }
 
@@ -4718,7 +4718,7 @@
         start_new_block(blockstart);
         llvm::BasicBlock *blockend = llvm::BasicBlock::Create(context, blockend_name);
         llvm::Function *fn = blockstart->getParent();
-        fn->getBasicBlockList().push_back(blockend);
+        fn->insert(fn->end(), blockend);
         builder->SetInsertPoint(blockstart);
         loop_or_block_end.push_back(blockend);
         loop_or_block_end_names.push_back(blockend_name);
--- a/src/libasr/codegen/evaluator.cpp
+++ b/src/libasr/codegen/evaluator.cpp
@@ -1,5 +1,6 @@
 #include <iostream>
 #include <fstream>
+#include <optional>
 
 #include <llvm/IR/LLVMContext.h>
 #include <llvm/ADT/STLExtras.h>
@@ -178,7 +179,7 @@
     std::string CPU = "generic";
     std::string features = "";
     llvm::TargetOptions opt;
-    llvm::Optional<llvm::Reloc::Model> RM = llvm::Reloc::Model::PIC_;
+    std::optional<llvm::Reloc::Model> RM = llvm::Reloc::Model::PIC_;
     TM = target->createTargetMachine(target_triple, CPU, features, opt, RM);
 
     // For some reason the JIT requires a different TargetMachine
--- a/src/libasr/codegen/llvm_utils.cpp
+++ b/src/libasr/codegen/llvm_utils.cpp
@@ -189,7 +189,7 @@
             // to our new block
             builder->CreateBr(bb);
         }
-        fn->getBasicBlockList().push_back(bb);
+        fn->insert(fn->end(), bb);
         builder->SetInsertPoint(bb);
     }