diff --git a/cmd/gomobile/build.go b/cmd/gomobile/build.go
index 8737210..6f5c7a4 100644
--- a/cmd/gomobile/build.go
+++ b/cmd/gomobile/build.go
@@ -50,8 +50,8 @@ are copied into the output.
 Flag -iosversion sets the minimal version of the iOS SDK to compile against.
 The default version is 6.1.
 
-The -bundleid flag is for -target ios only and sets the bundle ID to use
-with the app; defaults to "org.golang.todo".
+The -bundleid flag is required for -target ios and sets the bundle ID to use
+with the app.
 
 The -o flag specifies the output file name. If not specified, the
 output file name depends on the package built.
@@ -134,6 +134,9 @@ func runBuild(cmd *command) (err error) {
 			}
 			return nil
 		}
+		if buildBundleID == "" {
+			return fmt.Errorf("-target=ios requires -bundleid set")
+		}
 		nmpkgs, err = goIOSBuild(pkg, buildBundleID, targetArchs)
 		if err != nil {
 			return err
@@ -240,7 +243,7 @@ func addBuildFlags(cmd *command) {
 	cmd.flag.StringVar(&buildGcflags, "gcflags", "", "")
 	cmd.flag.StringVar(&buildLdflags, "ldflags", "", "")
 	cmd.flag.StringVar(&buildTarget, "target", "android", "")
-	cmd.flag.StringVar(&buildBundleID, "bundleid", "org.golang.todo", "")
+	cmd.flag.StringVar(&buildBundleID, "bundleid", "", "")
 	cmd.flag.StringVar(&buildIOSVersion, "iosversion", "6.1", "")
 
 	cmd.flag.BoolVar(&buildA, "a", false, "")
diff --git a/cmd/gomobile/doc.go b/cmd/gomobile/doc.go
index 059e4d8..7bcbc27 100644
--- a/cmd/gomobile/doc.go
+++ b/cmd/gomobile/doc.go
@@ -106,8 +106,8 @@ are copied into the output.
 Flag -iosversion sets the minimal version of the iOS SDK to compile against.
 The default version is 6.1.
 
-The -bundleid flag is for -target ios only and sets the bundle ID to use
-with the app; defaults to "org.golang.todo".
+The -bundleid flag is required for -target ios and sets the bundle ID to use
+with the app.
 
 The -o flag specifies the output file name. If not specified, the
 output file name depends on the package built.