diff --git a/clang-tools-extra/clangd/Config.h b/clang-tools-extra/clangd/Config.h
--- a/clang-tools-extra/clangd/Config.h
+++ b/clang-tools-extra/clangd/Config.h
@@ -106,7 +106,7 @@
     /// Enable emitting diagnostics using stale preambles.
     bool AllowStalePreamble = false;
 
-    IncludesPolicy UnusedIncludes = IncludesPolicy::None;
+    IncludesPolicy UnusedIncludes = IncludesPolicy::Strict;
     IncludesPolicy MissingIncludes = IncludesPolicy::None;
 
     /// IncludeCleaner will not diagnose usages of these headers matched by
diff --git a/clang-tools-extra/clangd/unittests/ConfigCompileTests.cpp b/clang-tools-extra/clangd/unittests/ConfigCompileTests.cpp
--- a/clang-tools-extra/clangd/unittests/ConfigCompileTests.cpp
+++ b/clang-tools-extra/clangd/unittests/ConfigCompileTests.cpp
@@ -246,10 +246,9 @@
 }
 
 TEST_F(ConfigCompileTests, DiagnosticsIncludeCleaner) {
-  // Defaults to None.
   EXPECT_TRUE(compileAndApply());
   EXPECT_EQ(Conf.Diagnostics.UnusedIncludes,
-            Config::IncludesPolicy::None);
+            Config::IncludesPolicy::Strict);
 
   Frag = {};
   Frag.Diagnostics.UnusedIncludes.emplace("None");
diff --git a/clang-tools-extra/clangd/unittests/IncludeCleanerTests.cpp b/clang-tools-extra/clangd/unittests/IncludeCleanerTests.cpp
--- a/clang-tools-extra/clangd/unittests/IncludeCleanerTests.cpp
+++ b/clang-tools-extra/clangd/unittests/IncludeCleanerTests.cpp
@@ -171,11 +171,6 @@
 }
 
 TEST(IncludeCleaner, GenerateMissingHeaderDiags) {
-  Config Cfg;
-  Cfg.Diagnostics.MissingIncludes = Config::IncludesPolicy::Strict;
-  Cfg.Diagnostics.Includes.IgnoreHeader = {
-      [](llvm::StringRef Header) { return Header.ends_with("buzz.h"); }};
-  WithContextValue Ctx(Config::Key, std::move(Cfg));
   Annotations MainFile(R"cpp(
 #include "a.h"
 #include "all.h"
@@ -247,6 +242,12 @@
   TU.Code = MainFile.code();
   ParsedAST AST = TU.build();
 
+  Config Cfg;
+  Cfg.Diagnostics.UnusedIncludes = Config::IncludesPolicy::None;
+  Cfg.Diagnostics.MissingIncludes = Config::IncludesPolicy::Strict;
+  Cfg.Diagnostics.Includes.IgnoreHeader = {
+      [](llvm::StringRef Header) { return Header.ends_with("buzz.h"); }};
+  WithContextValue Ctx(Config::Key, std::move(Cfg));
   std::vector<clangd::Diag> Diags =
       issueIncludeCleanerDiagnostics(AST, TU.Code);
   EXPECT_THAT(
@@ -308,9 +309,7 @@
     // IWYU pragma: private, include "public.h"
     void foo() {}
   )cpp");
-  Config Cfg;
-  Cfg.Diagnostics.UnusedIncludes = Config::IncludesPolicy::Strict;
-  WithContextValue Ctx(Config::Key, std::move(Cfg));
+  TU.Cfg.Diagnostics.UnusedIncludes = Config::IncludesPolicy::Strict;
   ParsedAST AST = TU.build();
   EXPECT_THAT(AST.getDiagnostics(), llvm::ValueIs(IsEmpty()));
   IncludeCleanerFindings Findings = computeIncludeCleanerFindings(AST);
@@ -356,11 +355,8 @@
   )cpp";
   TU.ExtraArgs.emplace_back("-xobjective-c");
 
-  Config Cfg;
-
-  Cfg.Diagnostics.UnusedIncludes = Config::IncludesPolicy::Strict;
-  Cfg.Diagnostics.MissingIncludes = Config::IncludesPolicy::Strict;
-  WithContextValue Ctx(Config::Key, std::move(Cfg));
+  TU.Cfg.Diagnostics.UnusedIncludes = Config::IncludesPolicy::Strict;
+  TU.Cfg.Diagnostics.MissingIncludes = Config::IncludesPolicy::Strict;
   ParsedAST AST = TU.build();
   EXPECT_THAT(AST.getDiagnostics(), llvm::ValueIs(IsEmpty()));
 }
@@ -375,9 +371,7 @@
     void foo() {}
   )cpp");
   TU.Filename = "public.h";
-  Config Cfg;
-  Cfg.Diagnostics.UnusedIncludes = Config::IncludesPolicy::Strict;
-  WithContextValue Ctx(Config::Key, std::move(Cfg));
+  TU.Cfg.Diagnostics.UnusedIncludes = Config::IncludesPolicy::Strict;
   ParsedAST AST = TU.build();
   EXPECT_THAT(AST.getDiagnostics(), llvm::ValueIs(IsEmpty()));
   IncludeCleanerFindings Findings = computeIncludeCleanerFindings(AST);