diff --git a/llvm_util/utils.h b/llvm_util/utils.h
index 491fd1484..7899ca2b3 100644
--- a/llvm_util/utils.h
+++ b/llvm_util/utils.h
@@ -3,8 +3,6 @@
 // Copyright (c) 2018-present The Alive2 Authors.
 // Distributed under the MIT license that can be found in the LICENSE file.
 
-#include "llvm/IR/Instructions.h"
-
 #include "ir/instr.h"
 #include <functional>
 #include <ostream>
@@ -13,6 +11,7 @@
 namespace llvm {
 class APInt;
 class BasicBlock;
+class CallInst;
 class ConstantExpr;
 class DataLayout;
 class Instruction;
@@ -71,7 +70,5 @@ std::unique_ptr<llvm::Module> openInputFile(llvm::LLVMContext &Context,
                                             const std::string &InputFilename);
 llvm::Function *findFunction(llvm::Module &M, const std::string &FName);
 
-bool are_tailcall_preconditions_met(const llvm::CallInst &i);
-
 IR::TailCallInfo parse_fn_tailcall(const llvm::CallInst &i);
 }