diff --git a/pkg/build/build.go b/pkg/build/build.go
index c9f9a419d..15e5508a4 100644
--- a/pkg/build/build.go
+++ b/pkg/build/build.go
@@ -33,6 +33,16 @@ var (
 	// BUNDLE_DIR is the directory where the bundle is located in the CNAB execution environment.
 	BUNDLE_DIR = "/cnab/app"
 
+	// BUNDLE_UID is the user id assigned to the user executing the bundle
+	BUNDLE_UID = 65532
+
+	// BUNDLE_GID is the group assigned to the user executing the bundle
+	// Defaults to root
+	BUNDLE_GID = 0
+
+	// BUNDLE_USER is the username assigned to the user executing the bundle
+	BUNDLE_USER="nonroot"
+
 	// PORTER_MIXINS_TOKEN can control where mixin instructions will be placed in
 	// Dockerfile.
 	PORTER_MIXINS_TOKEN = "# PORTER_MIXINS"
diff --git a/pkg/build/dockerfile-generator.go b/pkg/build/dockerfile-generator.go
index df131251d..860924ebe 100644
--- a/pkg/build/dockerfile-generator.go
+++ b/pkg/build/dockerfile-generator.go
@@ -192,9 +192,9 @@ func (g *DockerfileGenerator) buildMixinsSection(ctx context.Context) ([]string,
 func (g *DockerfileGenerator) buildInitSection() []string {
 	return []string{
 		"ARG BUNDLE_DIR",
-		"ARG BUNDLE_UID=65532",
-		"ARG BUNDLE_USER=nonroot",
-		"ARG BUNDLE_GID=0",
+		fmt.Sprintf("ARG BUNDLE_UID=%d", BUNDLE_UID),
+		fmt.Sprintf("ARG BUNDLE_USER=%s", BUNDLE_USER),
+		fmt.Sprintf("ARG BUNDLE_GID=%d", BUNDLE_GID),
 		// Create a non-root user that is in the root group with the specified id and a home directory
 		"RUN useradd ${BUNDLE_USER} -m -u ${BUNDLE_UID} -g ${BUNDLE_GID} -o",
 	}