diff --git a/functions/concrete/run/env/env_test.go b/functions/concrete/run/env/env_test.go
new file mode 100644
index 00000000..5607cf31
--- /dev/null
+++ b/functions/concrete/run/env/env_test.go
@@ -0,0 +1,19 @@
+//go:build !integration
+
+package env
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestExpandValue_GitLabEnvTakesPriorityOverEnv(t *testing.T) {
+	e := &Env{
+		Env:       map[string]string{"MY_VAR": "static"},
+		GitLabEnv: map[string]string{"MY_VAR": "dynamic"},
+	}
+
+	assert.Equal(t, "dynamic", e.ExpandValue("$MY_VAR"),
+		"GitLabEnv overlay must shadow Env for the same key")
+}