--- a/clang_delta/ExpressionDetector.cpp
+++ b/clang_delta/ExpressionDetector.cpp
@@ -62,9 +62,20 @@ public:
   virtual void InclusionDirective(SourceLocation HashLoc,
                           const Token &IncludeTok,
                           StringRef FileName, bool IsAngled,
-                          CharSourceRange FilenameRange, OptionalFileEntryRef File,
+                          CharSourceRange FilenameRange,
+#if LLVM_VERSION_MAJOR < 15
+                          const FileEntry *File,
+#elif LLVM_VERSION_MAJOR < 16
+                          Optional<FileEntryRef> File,
+#else
+                          OptionalFileEntryRef File,
+#endif
                           StringRef SearchPath, StringRef RelativePath,
+#if LLVM_VERSION_MAJOR < 19
                           const Module *Imported,
+#else
+                          const Module *SuggestedModule, bool ModuleImported,
+#endif
                           SrcMgr::CharacteristicKind FileType) override;
 
 private:
@@ -80,12 +91,22 @@ private:
 void IncludesPPCallbacks::InclusionDirective(SourceLocation HashLoc,
                                              const Token &/*IncludeTok*/,
                                              StringRef FileName,
-                                            bool /*IsAngled*/,
+                                             bool /*IsAngled*/,
                                              CharSourceRange /*FilenameRange*/,
+#if LLVM_VERSION_MAJOR < 15
+                                             const FileEntry * /*File*/,
+#elif LLVM_VERSION_MAJOR < 16
+                                             Optional<FileEntryRef> /*File*/,
+#else
                                              OptionalFileEntryRef /*File*/,
+#endif
                                              StringRef /*SearchPath*/,
                                              StringRef /*RelativePath*/,
-                                             const Module * /*Imported*/,
+#if LLVM_VERSION_MAJOR < 19
+                                            const Module *Imported,
+#else
+                                            const Module *SuggestedModule, bool ModuleImported,
+#endif
                                              SrcMgr::CharacteristicKind /*FileType*/)
 {
   if (!SrcManager.isInMainFile(HashLoc))
@@ -118,7 +139,11 @@ bool LocalTmpVarCollector::VisitDeclRefE
   const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl());
   if (!VD)
     return true;
+#if LLVM_VERSION_MAJOR < 18
   if (VD->getName().startswith(Prefix))
+#else
+  if (VD->getName().starts_with(Prefix))
+#endif
     TmpVars.push_back(VD);
   return true;
 }
@@ -363,7 +388,11 @@ void ExpressionDetector::addOneTempVar(c
 {
   if (!VD)
     return;
+#if LLVM_VERSION_MAJOR < 18
   if (!VD->getName().startswith(TmpVarNamePrefix))
+#else
+  if (!VD->getName().starts_with(TmpVarNamePrefix))
+#endif
     return;
   if (const Expr *E = VD->getInit())
     ProcessedExprs[VD] = E->IgnoreParenImpCasts();
@@ -374,9 +403,15 @@ bool ExpressionDetector::refToTmpVar(con
   StringRef Name = ND->getName();
   // We don't want to repeatly replace temporary variables
   // __creduce_expr_tmp_xxx, __creduce_printed_yy and __creduce_checked_zzz.
+#if LLVM_VERSION_MAJOR < 18
   return Name.startswith(TmpVarNamePrefix) ||
          Name.startswith(PrintedVarNamePrefix) ||
          Name.startswith(CheckedVarNamePrefix);
+#else
+  return Name.starts_with(TmpVarNamePrefix) ||
+         Name.starts_with(PrintedVarNamePrefix) ||
+         Name.starts_with(CheckedVarNamePrefix);
+#endif
 }
 
 // Reference: IdenticalExprChecker.cpp from Clang
@@ -524,8 +559,13 @@ bool ExpressionDetector::isValidExpr(Stm
       if (const DeclRefExpr *SubE =
           dyn_cast<DeclRefExpr>(UO->getSubExpr()->IgnoreParenCasts())) {
         StringRef SubEName = SubE->getDecl()->getName();
+#if LLVM_VERSION_MAJOR < 18
         if (SubEName.startswith(PrintedVarNamePrefix) ||
             SubEName.startswith(CheckedVarNamePrefix))
+#else
+        if (SubEName.starts_with(PrintedVarNamePrefix) ||
+            SubEName.starts_with(CheckedVarNamePrefix))
+#endif
           return false;
       }
     }
@@ -541,7 +581,11 @@ bool ExpressionDetector::isValidExpr(Stm
       bool IsLit = SC == Stmt::IntegerLiteralClass ||
                    SC == Stmt::FloatingLiteralClass;
       if (IsLit && DRE &&
+#if LLVM_VERSION_MAJOR < 18
           DRE->getDecl()->getName().startswith(TmpVarNamePrefix) &&
+#else
+          DRE->getDecl()->getName().starts_with(TmpVarNamePrefix) &&
+#endif
           S->getStmtClass() == Stmt::IfStmtClass) {
         return false;
       }
--- a/clang_delta/RemoveNamespace.cpp
+++ b/clang_delta/RemoveNamespace.cpp
@@ -944,7 +944,11 @@ void RemoveNamespace::handleOneNamedDecl
     TransAssert(IdInfo && "Invalid IdentifierInfo!");
     NewName += IdInfo->getName();
     // Make sure we have valid suffix for user literals
+#if LLVM_VERSION_MAJOR < 18
     if (IsUserLiteral && IdInfo->getName().startswith("_")) {
+#else
+    if (IsUserLiteral && IdInfo->getName().starts_with("_")) {
+#endif
       NewName = "_" + NewName;
     }
     NamedDeclToNewName[ND] = NewName;
--- a/clang_delta/CommonRenameClassRewriteVisitor.h
+++ b/clang_delta/CommonRenameClassRewriteVisitor.h
@@ -368,6 +368,9 @@ bool CommonRenameClassRewriteVisitor<T>:
   case TemplateArgument::Null:
   case TemplateArgument::Declaration:
   case TemplateArgument::Integral:
+#if LLVM_VERSION_MAJOR >= 18
+  case TemplateArgument::StructuralValue:
+#endif
     return true;
 
   case TemplateArgument::Type: {
--- a/clang_delta/RenameCXXMethod.cpp
+++ b/clang_delta/RenameCXXMethod.cpp
@@ -426,7 +426,7 @@ bool RenameCXXMethod::isValidName(const
 {
   size_t PrefixLen = MethodNamePrefix.length();
   StringRef NamePrefix = Name.substr(0, PrefixLen);
-  if (!NamePrefix.equals(MethodNamePrefix))
+  if (NamePrefix != MethodNamePrefix)
     return false;
   llvm::APInt Num;
   return !Name.drop_front(PrefixLen).getAsInteger(10, Num);