diff --git a/proto/swift_proto_utils.bzl b/proto/swift_proto_utils.bzl
index 56fc6f55d..cf85d4e78 100644
--- a/proto/swift_proto_utils.bzl
+++ b/proto/swift_proto_utils.bzl
@@ -37,6 +37,7 @@ load(
 # buildifier: disable=bzl-visibility
 load(
     "//swift/internal:utils.bzl",
+    "expand_make_variables",
     "get_providers",
     "include_developer_search_paths",
 )
@@ -258,12 +259,18 @@ def compile_swift_protos_for_target(
         unsupported_features = ctx.disabled_features,
     )
 
+    # These can't use additional_inputs since expand_locations needs targets,
+    # not files.
+    copts = expand_make_variables(ctx, getattr(attr, "copts", []), "copts")
+    linkopts = expand_make_variables(ctx, getattr(attr, "linkopts", []), "linkopts")
+
     # Compile the generated Swift source files as a module:
     include_dev_srch_paths = include_developer_search_paths(attr)
     compile_result = swift_common.compile(
         actions = ctx.actions,
         cc_infos = get_providers(compiler_deps, CcInfo),
-        copts = ["-parse-as-library"] + getattr(attr, "copts", []),
+        defines = ctx.attr.defines,
+        copts = ["-parse-as-library"] + copts,
         feature_configuration = feature_configuration,
         include_dev_srch_paths = include_dev_srch_paths,
         module_name = module_name,
@@ -294,6 +301,7 @@ def compile_swift_protos_for_target(
             ],
             module_context = module_context,
             swift_toolchain = swift_toolchain,
+            user_link_flags = linkopts,
         )
     )