diff --git a/clang-tools-extra/clangd/CodeComplete.cpp b/clang-tools-extra/clangd/CodeComplete.cpp
--- a/clang-tools-extra/clangd/CodeComplete.cpp
+++ b/clang-tools-extra/clangd/CodeComplete.cpp
@@ -1072,6 +1072,10 @@
   FrontendOpts.SkipFunctionBodies = true;
   // Disable typo correction in Sema.
   CI->getLangOpts()->SpellChecking = false;
+  // Code completion won't trigger in delayed template bodies.
+  // This is on-by-default in windows to allow parsing SDK headers; we're only
+  // disabling it for the main-file (not preamble).
+  CI->getLangOpts()->DelayedTemplateParsing = false;
   // Setup code completion.
   FrontendOpts.CodeCompleteOpts = Options;
   FrontendOpts.CodeCompletionAt.FileName = std::string(Input.FileName);
diff --git a/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp b/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
--- a/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
+++ b/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
@@ -127,7 +127,6 @@
   Annotations Test(Text);
   auto TU = TestTU::withCode(Test.code());
   // To make sure our tests for completiopns inside templates work on Windows.
-  TU.ExtraArgs = {"-fno-delayed-template-parsing"};
   TU.Filename = FilePath.str();
   return completions(TU, Test.point(), std::move(IndexSymbols),
                      std::move(Opts));
@@ -2660,6 +2659,20 @@
   EXPECT_THAT(Signatures, Contains(Sig("x() -> auto")));
 }
 
+TEST(CompletionTest, DelayedTemplateParsing) {
+  Annotations Test(R"cpp(
+    int xxx;
+    template <typename T> int foo() { return xx^; }
+  )cpp");
+  auto TU = TestTU::withCode(Test.code());
+  // Even though delayed-template-parsing is on, we will disable it to provide
+  // completion in templates.
+  TU.ExtraArgs.push_back("-fdelayed-template-parsing");
+
+  EXPECT_THAT(completions(TU, Test.point()).Completions,
+              Contains(Named("xxx")));
+}
+
 TEST(CompletionTest, CompletionRange) {
   const char *WithRange = "auto x = [[abc]]^";
   auto Completions = completions(WithRange);