diff --git a/docs/reference.md b/docs/reference.md
index 81f58e8..a9fad5b 100644
--- a/docs/reference.md
+++ b/docs/reference.md
@@ -3826,6 +3826,20 @@
         would be
           "-Wl,-add_ast_path,obj/foo/Foo.swiftmodule"
 
+    rust_swiftmodule_switch [string, optional, link tools only]
+        Valid for: Linker tools except "alink"
+
+        Like swiftmodule_switch, but for targets built/linked with the Rust
+        compiler. The string will be prependend to the path to the
+        .swiftmodule files that are embedded in the linker output.
+
+        If you specified:
+          rust_swiftmodule_swift = "-Clink-arg=-Wl,-add_ast_path,"
+        then the "{{swiftmodules}}" expansion for
+          [ "obj/foo/Foo.swiftmodule" ]
+        would be
+          "-Clink-arg=-Wl,-add_ast_path,obj/foo/Foo.swiftmodule"
+
     outputs  [list of strings with substitutions]
         Valid for: Linker and compiler tools (required)
 
diff --git a/src/gn/json_project_writer_unittest.cc b/src/gn/json_project_writer_unittest.cc
index b581051..a026b40 100644
--- a/src/gn/json_project_writer_unittest.cc
+++ b/src/gn/json_project_writer_unittest.cc
@@ -163,7 +163,8 @@
             "lib_dir_switch": "-Lnative=",
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
-            "outputs": [ "{{root_out_dir}}/{{crate_name}}{{output_extension}}" ]
+            "outputs": [ "{{root_out_dir}}/{{crate_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_cdylib": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -174,7 +175,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_dylib": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -185,7 +187,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_macro": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -196,7 +199,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_rlib": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -207,7 +211,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_staticlib": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -218,7 +223,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "solink": {
             "command": "ld -shared -o {{target_output_name}}.so {{inputs}} {{ldflags}} {{libs}}",
@@ -388,7 +394,8 @@
             "lib_dir_switch": "-Lnative=",
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
-            "outputs": [ "{{root_out_dir}}/{{crate_name}}{{output_extension}}" ]
+            "outputs": [ "{{root_out_dir}}/{{crate_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_cdylib": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -399,7 +406,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_dylib": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -410,7 +418,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_macro": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -421,7 +430,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_rlib": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -432,7 +442,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_staticlib": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -443,7 +454,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "solink": {
             "command": "ld -shared -o {{target_output_name}}.so {{inputs}} {{ldflags}} {{libs}}",
@@ -637,7 +649,8 @@
             "lib_dir_switch": "-Lnative=",
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
-            "outputs": [ "{{root_out_dir}}/{{crate_name}}{{output_extension}}" ]
+            "outputs": [ "{{root_out_dir}}/{{crate_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_cdylib": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -648,7 +661,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_dylib": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -659,7 +673,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_macro": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -670,7 +685,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_rlib": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -681,7 +697,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "rust_staticlib": {
             "command": "{{rustenv}} rustc --crate-name {{crate_name}} {{source}} --crate-type {{crate_type}} {{rustflags}} -o {{output}} {{rustdeps}} {{externs}}",
@@ -692,7 +709,8 @@
             "lib_switch": "-l",
             "linker_arg": "-Clink-arg=",
             "output_prefix": "lib",
-            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ]
+            "outputs": [ "{{target_out_dir}}/{{target_output_name}}{{output_extension}}" ],
+            "weak_framework_switch": "-lframework="
          },
          "solink": {
             "command": "ld -shared -o {{target_output_name}}.so {{inputs}} {{ldflags}} {{libs}}",
diff --git a/src/gn/ninja_rust_binary_target_writer.cc b/src/gn/ninja_rust_binary_target_writer.cc
index a400cf7..879e70d 100644
--- a/src/gn/ninja_rust_binary_target_writer.cc
+++ b/src/gn/ninja_rust_binary_target_writer.cc
@@ -141,12 +141,19 @@
 
   std::vector<OutputFile> rustdeps;
   std::vector<OutputFile> nonrustdeps;
+  std::vector<OutputFile> swiftmodules;
   nonrustdeps.insert(nonrustdeps.end(),
                      classified_deps.extra_object_files.begin(),
                      classified_deps.extra_object_files.end());
   for (const auto* framework_dep : classified_deps.framework_deps) {
     order_only_deps.push_back(framework_dep->dependency_output_file());
   }
+  if (target_->IsFinal()) {
+    for (const Target* dep : classified_deps.swiftmodule_deps) {
+      swiftmodules.push_back(dep->swift_values().module_output_file());
+      order_only_deps.push_back(dep->swift_values().module_output_file());
+    }
+  }
   for (const auto* non_linkable_dep : classified_deps.non_linkable_deps) {
     if (non_linkable_dep->source_types_used().RustSourceUsed() &&
         non_linkable_dep->output_type() != Target::SOURCE_SET) {
@@ -210,7 +217,8 @@
             classified_deps.non_linkable_deps.end(),
             std::back_inserter(extern_deps));
 
-  WriteExternsAndDeps(extern_deps, transitive_crates, rustdeps, nonrustdeps);
+  WriteExternsAndDeps(extern_deps, transitive_crates, rustdeps, nonrustdeps,
+                      swiftmodules);
   WriteSourcesAndInputs();
   WritePool(out_);
 }
@@ -259,7 +267,8 @@
     const std::vector<const Target*>& deps,
     const std::vector<ExternCrate>& transitive_rust_deps,
     const std::vector<OutputFile>& rustdeps,
-    const std::vector<OutputFile>& nonrustdeps) {
+    const std::vector<OutputFile>& nonrustdeps,
+    const std::vector<OutputFile>& swiftmodules) {
   // Writes a external LibFile which comes from user-specified externs, and may
   // be either a string or a SourceFile.
   auto write_extern_lib_file = [this](std::string_view crate_name,
@@ -382,6 +391,8 @@
   // If rustc will invoke a linker, all libraries need the passed through to the
   // linker.
   WriteLibs(out_, tool_);
+  WriteFrameworks(out_, tool_);
+  WriteSwiftModules(out_, tool_, swiftmodules);
 
   out_ << std::endl;
   out_ << "  ldflags =";
diff --git a/src/gn/ninja_rust_binary_target_writer.h b/src/gn/ninja_rust_binary_target_writer.h
index 69ec916..83e1203 100644
--- a/src/gn/ninja_rust_binary_target_writer.h
+++ b/src/gn/ninja_rust_binary_target_writer.h
@@ -31,7 +31,8 @@
   void WriteExternsAndDeps(const std::vector<const Target*>& deps,
                            const std::vector<ExternCrate>& transitive_rust_deps,
                            const std::vector<OutputFile>& rustdeps,
-                           const std::vector<OutputFile>& nonrustdeps);
+                           const std::vector<OutputFile>& nonrustdeps,
+                           const std::vector<OutputFile>& swiftmodules);
   // Unlike C/C++, Rust compiles all sources of a crate in one command.
   // Write a ninja variable `sources` that contains all sources and input files.
   void WriteSourcesAndInputs();
diff --git a/src/gn/ninja_rust_binary_target_writer_unittest.cc b/src/gn/ninja_rust_binary_target_writer_unittest.cc
index e3468a9..8ef944f 100644
--- a/src/gn/ninja_rust_binary_target_writer_unittest.cc
+++ b/src/gn/ninja_rust_binary_target_writer_unittest.cc
@@ -1963,3 +1963,130 @@
   std::string out_str = out.str();
   EXPECT_EQ(expected, out_str) << expected << "\n" << out_str;
 }
+
+// Tests frameworks are applied.
+TEST_F(NinjaRustBinaryTargetWriterTest, FrameworksAndFrameworkDirs) {
+  Err err;
+  TestWithScope setup;
+
+  // A config that force linking with the framework.
+  Config framework_config(setup.settings(),
+                          Label(SourceDir("//bar"), "framework_config"));
+  framework_config.visibility().SetPublic();
+  framework_config.own_values().frameworks().push_back("Bar.framework");
+  framework_config.own_values().framework_dirs().push_back(
+      SourceDir("//out/Debug/"));
+  ASSERT_TRUE(framework_config.OnResolved(&err));
+
+  // A target creating a framework bundle.
+  Target framework(setup.settings(), Label(SourceDir("//bar"), "framework"));
+  framework.set_output_type(Target::CREATE_BUNDLE);
+  framework.bundle_data().product_type() = "com.apple.product-type.framework";
+  framework.public_configs().push_back(LabelConfigPair(&framework_config));
+  framework.SetToolchain(setup.toolchain());
+  framework.visibility().SetPublic();
+  ASSERT_TRUE(framework.OnResolved(&err));
+
+  Target target(setup.settings(), Label(SourceDir("//linked/"), "exe"));
+  target.set_output_type(Target::EXECUTABLE);
+  target.visibility().SetPublic();
+  SourceFile main("//linked/exe.rs");
+  target.sources().push_back(main);
+  target.source_types_used().Set(SourceFile::SOURCE_RS);
+  target.rust_values().set_crate_root(main);
+  target.rust_values().crate_name() = "exe";
+  target.private_deps().push_back(LabelTargetPair(&framework));
+  target.config_values().frameworks().push_back("System.framework");
+  target.config_values().weak_frameworks().push_back("Whizbang.framework");
+  target.SetToolchain(setup.toolchain());
+  ASSERT_TRUE(target.OnResolved(&err));
+
+  std::ostringstream out;
+  NinjaRustBinaryTargetWriter writer(&target, out);
+  writer.Run();
+
+  const char expected[] =
+      "crate_name = exe\n"
+      "crate_type = bin\n"
+      "output_extension = \n"
+      "output_dir = \n"
+      "rustflags =\n"
+      "rustenv =\n"
+      "root_out_dir = .\n"
+      "target_gen_dir = gen/linked\n"
+      "target_out_dir = obj/linked\n"
+      "target_output_name = exe\n"
+      "\n"
+      "build ./exe: rust_bin ../../linked/exe.rs | ../../linked/exe.rs || "
+      "obj/bar/framework.stamp obj/bar/framework.stamp\n"
+      "  source_file_part = exe.rs\n"
+      "  source_name_part = exe\n"
+      "  externs =\n"
+      "  rustdeps = -Lframework=. -lframework=System -lframework=Bar "
+      "-lframework=Whizbang\n"
+      "  ldflags =\n"
+      "  sources = ../../linked/exe.rs\n";
+  const std::string out_str = out.str();
+  EXPECT_EQ(expected, out_str) << expected << "\n" << out_str;
+}
+
+// Test linking of targets containing Swift modules.
+TEST_F(NinjaRustBinaryTargetWriterTest, SwiftModule) {
+  Err err;
+  TestWithScope setup;
+
+  // A single Swift module.
+  Target foo_target(setup.settings(), Label(SourceDir("//foo/"), "foo"));
+  foo_target.set_output_type(Target::SOURCE_SET);
+  foo_target.visibility().SetPublic();
+  foo_target.sources().push_back(SourceFile("//foo/file1.swift"));
+  foo_target.sources().push_back(SourceFile("//foo/file2.swift"));
+  foo_target.source_types_used().Set(SourceFile::SOURCE_SWIFT);
+  foo_target.swift_values().module_name() = "Foo";
+  foo_target.SetToolchain(setup.toolchain());
+  ASSERT_TRUE(foo_target.OnResolved(&err));
+
+  // Rust target links with module.
+  Target target(setup.settings(), Label(SourceDir("//linked/"), "exe"));
+  target.set_output_type(Target::EXECUTABLE);
+  target.visibility().SetPublic();
+  SourceFile main("//linked/exe.rs");
+  target.sources().push_back(main);
+  target.source_types_used().Set(SourceFile::SOURCE_RS);
+  target.rust_values().set_crate_root(main);
+  target.rust_values().crate_name() = "exe";
+  target.private_deps().push_back(LabelTargetPair(&foo_target));
+  target.SetToolchain(setup.toolchain());
+  ASSERT_TRUE(target.OnResolved(&err));
+
+  std::ostringstream out;
+  NinjaRustBinaryTargetWriter writer(&target, out);
+  writer.Run();
+
+  const char expected[] =
+      "crate_name = exe\n"
+      "crate_type = bin\n"
+      "output_extension = \n"
+      "output_dir = \n"
+      "rustflags =\n"
+      "rustenv =\n"
+      "root_out_dir = .\n"
+      "target_gen_dir = gen/linked\n"
+      "target_out_dir = obj/linked\n"
+      "target_output_name = exe\n"
+      "\n"
+      "build ./exe: rust_bin ../../linked/exe.rs | ../../linked/exe.rs "
+      "obj/foo/file1.o obj/foo/file2.o || "
+      "obj/foo/foo.stamp obj/foo/Foo.swiftmodule obj/foo/foo.stamp\n"
+      "  source_file_part = exe.rs\n"
+      "  source_name_part = exe\n"
+      "  externs =\n"
+      "  rustdeps = -Lnative=obj/foo -Clink-arg=-Bdynamic "
+      "-Clink-arg=obj/foo/file1.o -Clink-arg=obj/foo/file2.o "
+      "-Clink-arg=-swiftmodule=obj/foo/Foo.swiftmodule\n"
+      "  ldflags =\n"
+      "  sources = ../../linked/exe.rs\n";
+
+  const std::string out_str = out.str();
+  EXPECT_EQ(expected, out_str) << expected << "\n" << out_str;
+}
diff --git a/src/gn/rust_tool.cc b/src/gn/rust_tool.cc
index 5b5cc62..f799d73 100644
--- a/src/gn/rust_tool.cc
+++ b/src/gn/rust_tool.cc
@@ -16,8 +16,15 @@
 
 RustTool::RustTool(const char* n) : Tool(n) {
   CHECK(ValidateName(n));
-  // TODO: should these be settable in toolchain definition?
+  // TODO: should these be settable in toolchain definition? They would collide
+  // with the same switch names for C tools, however. So reading them from the
+  // toolchain definition would produce the incorrect switch unless we separate
+  // their names somehow.
   set_framework_switch("-lframework=");
+  // NOTE: No support for weak_framework in rustc, so we just use `-lframework`
+  // for now, to avoid more cryptic compiler errors.
+  // https://doc.rust-lang.org/rustc/command-line-arguments.html#-l-link-the-generated-crate-to-a-native-library
+  set_weak_framework_switch("-lframework=");
   set_framework_dir_switch("-Lframework=");
   set_lib_dir_switch("-Lnative=");
   set_lib_switch("-l");
@@ -119,7 +126,9 @@
   }
 
   if (MayLink()) {
-    if (!ReadString(scope, "dynamic_link_switch", &dynamic_link_switch_, err)) {
+    if (!ReadString(scope, "rust_swiftmodule_switch", &swiftmodule_switch_,
+                    err) ||
+        !ReadString(scope, "dynamic_link_switch", &dynamic_link_switch_, err)) {
       return false;
     }
   }
diff --git a/src/gn/test_with_scope.cc b/src/gn/test_with_scope.cc
index 4f33a59..1fae377 100644
--- a/src/gn/test_with_scope.cc
+++ b/src/gn/test_with_scope.cc
@@ -229,6 +229,7 @@
       rustc_tool.get());
   rustc_tool->set_outputs(SubstitutionList::MakeForTest(
       "{{root_out_dir}}/{{crate_name}}{{output_extension}}"));
+  rustc_tool->set_swiftmodule_switch("-Clink-arg=-swiftmodule=");
   toolchain->SetTool(std::move(rustc_tool));
 
   // SWIFT
@@ -254,6 +255,7 @@
   cdylib_tool->set_default_output_extension(".so");
   cdylib_tool->set_outputs(SubstitutionList::MakeForTest(
       "{{target_out_dir}}/{{target_output_name}}{{output_extension}}"));
+  cdylib_tool->set_swiftmodule_switch("-Clink-arg=-swiftmodule=");
   toolchain->SetTool(std::move(cdylib_tool));
 
   // RUST DYLIB
@@ -267,6 +269,7 @@
   dylib_tool->set_default_output_extension(".so");
   dylib_tool->set_outputs(SubstitutionList::MakeForTest(
       "{{target_out_dir}}/{{target_output_name}}{{output_extension}}"));
+  dylib_tool->set_swiftmodule_switch("-Clink-arg=-swiftmodule=");
   toolchain->SetTool(std::move(dylib_tool));
 
   // RUST_PROC_MACRO
@@ -281,6 +284,7 @@
   rust_proc_macro_tool->set_default_output_extension(".so");
   rust_proc_macro_tool->set_outputs(SubstitutionList::MakeForTest(
       "{{target_out_dir}}/{{target_output_name}}{{output_extension}}"));
+  rust_proc_macro_tool->set_swiftmodule_switch("-Clink-arg=-swiftmodule=");
   toolchain->SetTool(std::move(rust_proc_macro_tool));
 
   // RLIB