diff --git a/doc/api.md b/doc/api.md
index 39eb56ce3..621656352 100644
--- a/doc/api.md
+++ b/doc/api.md
@@ -163,7 +163,7 @@ A `struct` with the following fields:
 ## swift_common.compile_module_interface
 
 <pre>
-swift_common.compile_module_interface(<a href="#swift_common.compile_module_interface-actions">actions</a>, <a href="#swift_common.compile_module_interface-compilation_contexts">compilation_contexts</a>, <a href="#swift_common.compile_module_interface-exec_group">exec_group</a>,
+swift_common.compile_module_interface(<a href="#swift_common.compile_module_interface-actions">actions</a>, <a href="#swift_common.compile_module_interface-compilation_contexts">compilation_contexts</a>, <a href="#swift_common.compile_module_interface-copts">copts</a>, <a href="#swift_common.compile_module_interface-exec_group">exec_group</a>,
                                       <a href="#swift_common.compile_module_interface-feature_configuration">feature_configuration</a>, <a href="#swift_common.compile_module_interface-module_name">module_name</a>, <a href="#swift_common.compile_module_interface-swiftinterface_file">swiftinterface_file</a>,
                                       <a href="#swift_common.compile_module_interface-swift_infos">swift_infos</a>, <a href="#swift_common.compile_module_interface-swift_toolchain">swift_toolchain</a>, <a href="#swift_common.compile_module_interface-target_name">target_name</a>)
 </pre>
@@ -177,6 +177,7 @@ Compiles a Swift module interface.
 | :------------- | :------------- | :------------- |
 | <a id="swift_common.compile_module_interface-actions"></a>actions |  The context's `actions` object.   |  none |
 | <a id="swift_common.compile_module_interface-compilation_contexts"></a>compilation_contexts |  A list of `CcCompilationContext`s that represent C/Objective-C requirements of the target being compiled, such as Swift-compatible preprocessor defines, header search paths, and so forth. These are typically retrieved from the `CcInfo` providers of a target's dependencies.   |  none |
+| <a id="swift_common.compile_module_interface-copts"></a>copts |  A list of compiler flags that apply to the target being built.   |  `[]` |
 | <a id="swift_common.compile_module_interface-exec_group"></a>exec_group |  Runs the Swift compilation action under the given execution group's context. If `None`, the default execution group is used.   |  `None` |
 | <a id="swift_common.compile_module_interface-feature_configuration"></a>feature_configuration |  A feature configuration obtained from `swift_common.configure_features`.   |  none |
 | <a id="swift_common.compile_module_interface-module_name"></a>module_name |  The name of the Swift module being compiled. This must be present and valid; use `swift_common.derive_module_name` to generate a default from the target's label if needed.   |  none |
diff --git a/swift/internal/compiling.bzl b/swift/internal/compiling.bzl
index a9796eb07..7a3dfa91a 100644
--- a/swift/internal/compiling.bzl
+++ b/swift/internal/compiling.bzl
@@ -205,6 +205,7 @@ def compile_module_interface(
         *,
         actions,
         compilation_contexts,
+        copts = [],
         exec_group = None,
         feature_configuration,
         module_name,
@@ -221,6 +222,7 @@ def compile_module_interface(
             Swift-compatible preprocessor defines, header search paths, and so
             forth. These are typically retrieved from the `CcInfo` providers of
             a target's dependencies.
+        copts: A list of compiler flags that apply to the target being built.
         exec_group: Runs the Swift compilation action under the given execution
             group's context. If `None`, the default execution group is used.
         feature_configuration: A feature configuration obtained from
@@ -323,7 +325,7 @@ def compile_module_interface(
         target_label = feature_configuration._label,
         transitive_modules = transitive_modules,
         transitive_swiftmodules = transitive_swiftmodules,
-        user_compile_flags = [],
+        user_compile_flags = copts,
         vfsoverlay_file = vfsoverlay_file,
         vfsoverlay_search_path = _SWIFTMODULES_VFS_ROOT,
     )