diff --git a/src/main/java/com/google/devtools/build/lib/runtime/CommandLineEvent.java b/src/main/java/com/google/devtools/build/lib/runtime/CommandLineEvent.java
index 97a6e924e758ed..bd1fbb8326bfca 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/CommandLineEvent.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/CommandLineEvent.java
@@ -145,6 +145,17 @@ private Option createOption(
       return option.build();
     }
 
+    Option createStarlarkOption(String starlarkFlag, @Nullable Object value) {
+      String combinedForm = String.format("--%s=%s", starlarkFlag, value);
+      Option.Builder option = Option.newBuilder();
+      option.setCombinedForm(combinedForm);
+      option.setOptionName(starlarkFlag);
+      if (value != null) {
+        option.setOptionValue(String.valueOf(value));
+      }
+      return option.build();
+    }
+
     /**
      * Returns the startup option section of the command line for the startup options as the server
      * received them at its startup. Since not all client options get passed to the server as
@@ -251,11 +262,16 @@ private CommandLineSection getExplicitCommandOptions() {
                       parsedOptionDescription.getPriority().getPriorityCategory()
                           == OptionPriority.PriorityCategory.COMMAND_LINE)
               .collect(Collectors.toList());
+      List<Option> starlarkOptions =
+          commandOptions.getStarlarkOptions().entrySet().stream()
+              .map(e -> createStarlarkOption(e.getKey(), e.getValue()))
+              .collect(Collectors.toList());
       return CommandLineSection.newBuilder()
           .setSectionLabel("command options")
           .setOptionList(
               OptionList.newBuilder()
-                  .addAllOption(getOptionListFromParsedOptionDescriptions(explicitOptions)))
+                  .addAllOption(getOptionListFromParsedOptionDescriptions(explicitOptions))
+                  .addAllOption(starlarkOptions))
           .build();
     }
 
diff --git a/src/test/java/com/google/devtools/build/lib/BUILD b/src/test/java/com/google/devtools/build/lib/BUILD
index 6ef27cf8820f10..0098676d0bbc6b 100644
--- a/src/test/java/com/google/devtools/build/lib/BUILD
+++ b/src/test/java/com/google/devtools/build/lib/BUILD
@@ -1282,6 +1282,7 @@ java_test(
         "//src/main/protobuf:command_line_java_proto",
         "//src/main/protobuf:invocation_policy_java_proto",
         "//src/main/protobuf:test_status_java_proto",
+        "//src/test/java/com/google/devtools/build/lib/skylark:testutil",
         "//src/test/java/com/google/devtools/common/options:testutils",
         "//third_party:apache_commons_lang",
         "//third_party:mockito",
diff --git a/src/test/java/com/google/devtools/build/lib/runtime/StarlarkOptionCommandLineEventTest.java b/src/test/java/com/google/devtools/build/lib/runtime/StarlarkOptionCommandLineEventTest.java
new file mode 100644
index 00000000000000..d53711246ce499
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/lib/runtime/StarlarkOptionCommandLineEventTest.java
@@ -0,0 +1,64 @@
+// Copyright 2019 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.google.devtools.build.lib.runtime;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.devtools.build.lib.bazel.BazelStartupOptionsModule.Options;
+import com.google.devtools.build.lib.runtime.CommandLineEvent.OriginalCommandLineEvent;
+import com.google.devtools.build.lib.runtime.proto.CommandLineOuterClass.CommandLine;
+import com.google.devtools.build.lib.skylark.util.StarlarkOptionsTestCase;
+import com.google.devtools.common.options.OptionsParser;
+import java.util.Optional;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/**
+ * Tests for {@link CommandLineEvent}'s construction of the command lines which contain
+ * Starlark-style flags.
+ */
+@RunWith(JUnit4.class)
+public class StarlarkOptionCommandLineEventTest extends StarlarkOptionsTestCase {
+
+  @Test
+  public void testStarlarkOptions() throws Exception {
+    OptionsParser fakeStartupOptions =
+        OptionsParser.builder()
+            .optionsClasses(BlazeServerStartupOptions.class, Options.class)
+            .build();
+
+    writeBasicIntFlag();
+
+    parseStarlarkOptions("--//test:my_int_setting=666");
+
+    CommandLine line =
+        new OriginalCommandLineEvent(
+                "testblaze", fakeStartupOptions, "someCommandName", optionsParser, Optional.empty())
+            .asStreamProto(null)
+            .getStructuredCommandLine();
+
+    // Command options should appear in section 3. See
+    // CommandLineEventTest#testOptionsAtVariousPriorities_OriginalCommandLine.
+    // Verify that the starlark flag was processed as expected.
+    assertThat(line.getSections(3).getOptionList().getOptionCount()).isEqualTo(1);
+    assertThat(line.getSections(3).getOptionList().getOption(0).getCombinedForm())
+        .isEqualTo("--//test:my_int_setting=666");
+    assertThat(line.getSections(3).getOptionList().getOption(0).getOptionName())
+        .isEqualTo("//test:my_int_setting");
+    assertThat(line.getSections(3).getOptionList().getOption(0).getOptionValue()).isEqualTo("666");
+  }
+
+  // TODO(katre): Test mix of regular and starlark flags.
+}
diff --git a/src/test/shell/integration/build_event_stream_test.sh b/src/test/shell/integration/build_event_stream_test.sh
index 26fc9ee4e43575..60ccd301b3d8dc 100755
--- a/src/test/shell/integration/build_event_stream_test.sh
+++ b/src/test/shell/integration/build_event_stream_test.sh
@@ -13,8 +13,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-#
-# An end-to-end test that Bazel's experimental UI produces reasonable output.
 
 # Load the test setup defined in the parent directory
 CURRENT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
@@ -944,4 +942,30 @@ function test_bep_report_only_important_artifacts() {
   rm bep.txt
 }
 
+function test_starlark_flags() {
+  cat >> build_setting.bzl <<EOF
+def _build_setting_impl(ctx):
+  return []
+int_setting = rule(
+  implementation = _build_setting_impl,
+  build_setting = config.int(flag=True)
+)
+EOF
+  cat >> BUILD <<EOF
+load('//:build_setting.bzl', 'int_setting')
+int_setting(name = 'my_int_setting',
+  build_setting_default = 42,
+)
+EOF
+
+  bazel build --build_event_text_file=bep.txt \
+    --//:my_int_setting=666 \
+    //pkg:true || fail "Build failed but should have succeeded"
+  cat bep.txt >> "$TEST_log"
+  rm bep.txt
+
+  expect_log 'option_name: "//:my_int_setting"'
+  expect_log 'option_value: "666"'
+}
+
 run_suite "Integration tests for the build event stream"