diff --git a/clang-tools-extra/clangd/Compiler.cpp b/clang-tools-extra/clangd/Compiler.cpp
--- a/clang-tools-extra/clangd/Compiler.cpp
+++ b/clang-tools-extra/clangd/Compiler.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "Compiler.h"
+#include "Config.h"
 #include "support/Logger.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Frontend/CompilerInvocation.h"
@@ -89,6 +90,11 @@
   CI.getLangOpts()->ProfileListFiles.clear();
   CI.getLangOpts()->XRayAlwaysInstrumentFiles.clear();
   CI.getLangOpts()->XRayNeverInstrumentFiles.clear();
+
+  if (!Config::current().CompileFlags.NaiveModules) {
+    CI.getLangOpts()->Modules = false;
+    CI.getLangOpts()->CPlusPlusModules = false;
+  }
 }
 
 std::unique_ptr<CompilerInvocation>
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
@@ -66,6 +66,8 @@
         Edits;
     /// Where to search for compilation databases for this file's flags.
     CDBSearchSpec CDBSearch = {CDBSearchSpec::Ancestors, std::nullopt};
+    /// Allow modules when enabled by -fmodules, -std=c++20, etc.
+    bool NaiveModules = true;
   } CompileFlags;
 
   enum class BackgroundPolicy { Build, Skip };
diff --git a/clang-tools-extra/clangd/ConfigCompile.cpp b/clang-tools-extra/clangd/ConfigCompile.cpp
--- a/clang-tools-extra/clangd/ConfigCompile.cpp
+++ b/clang-tools-extra/clangd/ConfigCompile.cpp
@@ -320,6 +320,12 @@
               C.CompileFlags.CDBSearch = Spec;
             });
     }
+
+    if (F.NaiveModules)
+      Out.Apply.push_back(
+          [NaiveModules(**F.NaiveModules)](const Params &, Config &C) {
+            C.CompileFlags.NaiveModules = NaiveModules;
+          });
   }
 
   void compile(Fragment::IndexBlock &&F) {
diff --git a/clang-tools-extra/clangd/ConfigFragment.h b/clang-tools-extra/clangd/ConfigFragment.h
--- a/clang-tools-extra/clangd/ConfigFragment.h
+++ b/clang-tools-extra/clangd/ConfigFragment.h
@@ -169,6 +169,11 @@
     /// - Ancestors: search all parent directories (the default)
     /// - std::nullopt: do not use a compilation database, just default flags.
     std::optional<Located<std::string>> CompilationDatabase;
+
+    /// Allow flags such as -fmodules or -std=c++20 to enable modules.
+    /// We don't support modules: https://github.com/clangd/clangd/issues/1293
+    /// However some configurations may happen to work anyway.
+    std::optional<Located<bool>> NaiveModules;
   };
   CompileFlagsBlock CompileFlags;
 
diff --git a/clang-tools-extra/clangd/ConfigYAML.cpp b/clang-tools-extra/clangd/ConfigYAML.cpp
--- a/clang-tools-extra/clangd/ConfigYAML.cpp
+++ b/clang-tools-extra/clangd/ConfigYAML.cpp
@@ -108,6 +108,9 @@
     Dict.handle("CompilationDatabase", [&](Node &N) {
       F.CompilationDatabase = scalarValue(N, "CompilationDatabase");
     });
+    Dict.handle("NaiveModules", [&](Node &N) {
+      F.NaiveModules = boolValue(N, "NaiveModules");
+    });
     Dict.parse(N);
   }
 
diff --git a/clang-tools-extra/clangd/unittests/FindSymbolsTests.cpp b/clang-tools-extra/clangd/unittests/FindSymbolsTests.cpp
--- a/clang-tools-extra/clangd/unittests/FindSymbolsTests.cpp
+++ b/clang-tools-extra/clangd/unittests/FindSymbolsTests.cpp
@@ -6,12 +6,15 @@
 //
 //===----------------------------------------------------------------------===//
 #include "Annotations.h"
+#include "Config.h"
 #include "FindSymbols.h"
 #include "TestFS.h"
 #include "TestTU.h"
+#include "support/Context.h"
 #include "llvm/ADT/StringRef.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include <utility>
 
 namespace clang {
 namespace clangd {
@@ -491,6 +494,10 @@
 }
 
 TEST(DocumentSymbols, ExportContext) {
+  Config EnableModules;
+  EnableModules.CompileFlags.NaiveModules = true;
+  WithContextValue WithCfg(Config::Key, std::move(EnableModules));
+
   TestTU TU;
   TU.ExtraArgs = {"-std=c++20"};
   TU.Code = R"cpp(
diff --git a/clang-tools-extra/clangd/unittests/ModulesTests.cpp b/clang-tools-extra/clangd/unittests/ModulesTests.cpp
--- a/clang-tools-extra/clangd/unittests/ModulesTests.cpp
+++ b/clang-tools-extra/clangd/unittests/ModulesTests.cpp
@@ -6,8 +6,10 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "Config.h"
 #include "TestFS.h"
 #include "TestTU.h"
+#include "support/Context.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 
@@ -18,7 +20,21 @@
 namespace clangd {
 namespace {
 
-TEST(Modules, TextualIncludeInPreamble) {
+enum class ModulesMode { Disabled, Naive };
+Config makeModuleConfig(ModulesMode M) {
+  Config EnableModules;
+  EnableModules.CompileFlags.NaiveModules = M == ModulesMode::Naive;
+  return EnableModules;
+}
+
+class ModulesTest : public ::testing::TestWithParam<ModulesMode> {
+  WithContextValue WithCfg;
+
+protected:
+  ModulesTest() : WithCfg(Config::Key, makeModuleConfig(GetParam())) {}
+};
+
+TEST_P(ModulesTest, TextualIncludeInPreamble) {
   TestTU TU = TestTU::withCode(R"cpp(
     #include "Textual.h"
 
@@ -40,7 +56,7 @@
 
 // Verify that visibility of AST nodes belonging to modules, but loaded from
 // preamble PCH, is restored.
-TEST(Modules, PreambleBuildVisibility) {
+TEST_P(ModulesTest, PreambleBuildVisibility) {
   TestTU TU = TestTU::withCode(R"cpp(
     #include "module.h"
 
@@ -63,7 +79,7 @@
   EXPECT_TRUE(TU.build().getDiagnostics().empty());
 }
 
-TEST(Modules, Diagnostic) {
+TEST_P(ModulesTest, Diagnostic) {
   // Produce a diagnostic while building an implicit module. Use
   // -fmodules-strict-decluse, but any non-silenced diagnostic will do.
   TestTU TU = TestTU::withCode(R"cpp(
@@ -92,7 +108,7 @@
 }
 
 // Unknown module formats are a fatal failure for clang. Ensure we don't crash.
-TEST(Modules, UnknownFormat) {
+TEST_P(ModulesTest, UnknownFormat) {
   TestTU TU = TestTU::withCode(R"(#include "modular.h")");
   TU.OverlayRealFileSystemForModules = true;
   TU.ExtraArgs.push_back("-Xclang");
@@ -109,6 +125,25 @@
   // Test that we do not crash.
   TU.build();
 }
+
+MATCHER_P(diag, M, "") { return arg.Message == M; }
+
+TEST_P(ModulesTest, Cpp20Import) {
+  TestTU TU = TestTU::withCode("import foo; // error-ok");
+  TU.ExtraArgs.push_back("-Xclang");
+  TU.ExtraArgs.push_back("-std=c++20");
+
+  auto AST = TU.build();
+  EXPECT_THAT(AST.getDiagnostics(),
+              testing::ElementsAre(GetParam() == ModulesMode::Naive
+                                       ? diag("module 'foo' not found")
+                                       : diag("unknown type name 'import'")));
+}
+
+INSTANTIATE_TEST_SUITE_P(ModulesTestModes, ModulesTest,
+                         testing::Values(ModulesMode::Disabled,
+                                         ModulesMode::Naive));
+
 } // namespace
 } // namespace clangd
 } // namespace clang
diff --git a/clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp b/clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp
--- a/clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp
@@ -7,9 +7,11 @@
 //===----------------------------------------------------------------------===//
 
 #include "Annotations.h"
+#include "Config.h"
 #include "TestFS.h"
 #include "TestTU.h"
 #include "index/SymbolCollector.h"
+#include "support/Context.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/FileSystemOptions.h"
 #include "clang/Frontend/CompilerInstance.h"
@@ -28,6 +30,7 @@
 #include <memory>
 #include <optional>
 #include <string>
+#include <utility>
 
 namespace clang {
 namespace clangd {
@@ -1918,6 +1921,10 @@
 
 // Regression test for a crash-bug we used to have.
 TEST_F(SymbolCollectorTest, UndefOfModuleMacro) {
+  Config EnableModules;
+  EnableModules.CompileFlags.NaiveModules = true;
+  WithContextValue WithCfg(Config::Key, std::move(EnableModules));
+
   auto TU = TestTU::withCode(R"cpp(#include "bar.h")cpp");
   TU.AdditionalFiles["bar.h"] = R"cpp(
     #include "foo.h"