diff --git a/src/clang_tu.cc b/src/clang_tu.cc
index 67f4856d..b78adf7c 100644
--- a/src/clang_tu.cc
+++ b/src/clang_tu.cc
@@ -163,10 +163,16 @@ buildCompilerInvocation(const std::string &main, std::vector<const char *> args,
   ci->getFrontendOpts().DisableFree = false;
   // Enable IndexFrontendAction::shouldSkipFunctionBody.
   ci->getFrontendOpts().SkipFunctionBodies = true;
+#if LLVM_VERSION_MAJOR >= 18
+  ci->getLangOpts().SpellChecking = false;
+  ci->getLangOpts().RecoveryAST = true;
+  ci->getLangOpts().RecoveryASTType = true;
+#else
   ci->getLangOpts()->SpellChecking = false;
 #if LLVM_VERSION_MAJOR >= 11
   ci->getLangOpts()->RecoveryAST = true;
   ci->getLangOpts()->RecoveryASTType = true;
+#endif
 #endif
   auto &isec = ci->getFrontendOpts().Inputs;
   if (isec.size())
diff --git a/src/indexer.cc b/src/indexer.cc
index 83b77a20..50bb299c 100644
--- a/src/indexer.cc
+++ b/src/indexer.cc
@@ -1294,9 +1294,15 @@ index(SemaManager *manager, WorkingFiles *wfiles, VFS *vfs,
   ok = false;
   // -fparse-all-comments enables documentation in the indexer and in
   // code completion.
+#if LLVM_VERSION_MAJOR >= 18
+  ci->getLangOpts().CommentOpts.ParseAllComments =
+      g_config->index.comments > 1;
+  ci->getLangOpts().RetainCommentsFromSystemHeaders = true;
+#else
   ci->getLangOpts()->CommentOpts.ParseAllComments =
       g_config->index.comments > 1;
   ci->getLangOpts()->RetainCommentsFromSystemHeaders = true;
+#endif
   std::string buf = wfiles->getContent(main);
   std::vector<std::unique_ptr<llvm::MemoryBuffer>> bufs;
   if (buf.size())
diff --git a/src/sema_manager.cc b/src/sema_manager.cc
index c6f803c3..6be9e60d 100644
--- a/src/sema_manager.cc
+++ b/src/sema_manager.cc
@@ -368,8 +368,12 @@ void buildPreamble(Session &session, CompilerInvocation &ci,
   std::unique_ptr<llvm::MemoryBuffer> buf =
       llvm::MemoryBuffer::getMemBuffer(content);
 #if LLVM_VERSION_MAJOR >= 12
+#if LLVM_VERSION_MAJOR >= 18
+  auto bounds = ComputePreambleBounds(ci.getLangOpts(), *buf, 0);
+#else
   // llvmorg-12-init-11522-g4c55c3b66de
   auto bounds = ComputePreambleBounds(*ci.getLangOpts(), *buf, 0);
+#endif
   // llvmorg-12-init-17739-gf4d02fbe418d
   if (!task.from_diag && oldP &&
       oldP->preamble.CanReuse(ci, *buf, bounds, *fs))
@@ -387,8 +391,13 @@ void buildPreamble(Session &session, CompilerInvocation &ci,
   ws.erase(std::remove(ws.begin(), ws.end(), "error"), ws.end());
   ci.getDiagnosticOpts().IgnoreWarnings = false;
   ci.getFrontendOpts().SkipFunctionBodies = true;
+#if LLVM_VERSION_MAJOR >= 18
+  ci.getLangOpts().CommentOpts.ParseAllComments = g_config->index.comments > 1;
+  ci.getLangOpts().RetainCommentsFromSystemHeaders = true;
+#else
   ci.getLangOpts()->CommentOpts.ParseAllComments = g_config->index.comments > 1;
   ci.getLangOpts()->RetainCommentsFromSystemHeaders = true;
+#endif
 
   StoreDiags dc(task.path);
   IntrusiveRefCntPtr<DiagnosticsEngine> de =
@@ -498,12 +507,19 @@ void *completionMain(void *manager_) {
     fOpts.CodeCompletionAt.FileName = task->path;
     fOpts.CodeCompletionAt.Line = task->position.line + 1;
     fOpts.CodeCompletionAt.Column = task->position.character + 1;
+#if LLVM_VERSION_MAJOR >= 18
+    ci->getLangOpts().CommentOpts.ParseAllComments = true;
+#else
     ci->getLangOpts()->CommentOpts.ParseAllComments = true;
+#endif
 
     DiagnosticConsumer dc;
     std::string content = manager->wfiles->getContent(task->path);
     auto buf = llvm::MemoryBuffer::getMemBuffer(content);
-#if LLVM_VERSION_MAJOR >= 12 // llvmorg-12-init-11522-g4c55c3b66de
+#if LLVM_VERSION_MAJOR >= 18
+    PreambleBounds bounds =
+        ComputePreambleBounds(ci->getLangOpts(), *buf, 0);
+#elif LLVM_VERSION_MAJOR >= 12 // llvmorg-12-init-11522-g4c55c3b66de
     PreambleBounds bounds =
         ComputePreambleBounds(*ci->getLangOpts(), *buf, 0);
 #else
@@ -601,7 +617,10 @@ void *diagnosticMain(void *manager_) {
       if (!rebuild) {
         std::string content = manager->wfiles->getContent(task.path);
         auto buf = llvm::MemoryBuffer::getMemBuffer(content);
-#if LLVM_VERSION_MAJOR >= 12 // llvmorg-12-init-11522-g4c55c3b66de
+#if LLVM_VERSION_MAJOR >= 18
+        PreambleBounds bounds =
+            ComputePreambleBounds(ci->getLangOpts(), *buf, 0);
+#elif LLVM_VERSION_MAJOR >= 12 // llvmorg-12-init-11522-g4c55c3b66de
         PreambleBounds bounds =
             ComputePreambleBounds(*ci->getLangOpts(), *buf, 0);
 #else
@@ -622,7 +641,11 @@ void *diagnosticMain(void *manager_) {
       ci->getDiagnosticOpts().Warnings.push_back("no-unused-function");
     ci->getDiagnosticOpts().IgnoreWarnings = false;
     ci->getFrontendOpts().SkipFunctionBodies = false;
+#if LLVM_VERSION_MAJOR >= 18
+    ci->getLangOpts().SpellChecking = g_config->diagnostics.spellChecking;
+#else
     ci->getLangOpts()->SpellChecking = g_config->diagnostics.spellChecking;
+#endif
     StoreDiags dc(task.path);
     std::string content = manager->wfiles->getContent(task.path);
     auto buf = llvm::MemoryBuffer::getMemBuffer(content);