diff --git a/tests/src/boxed_field.rs b/tests/src/boxed_field.rs
new file mode 100644
index 000000000..b41b7735c
--- /dev/null
+++ b/tests/src/boxed_field.rs
@@ -0,0 +1,10 @@
+include!(concat!(env!("OUT_DIR"), "/boxed_field.rs"));
+
+#[test]
+/// Confirm `Foo::bar` is boxed by creating an instance
+fn test_bar_is_boxed() {
+    use alloc::boxed::Box;
+    let _ = Foo {
+        bar: Some(Box::new(Bar {})),
+    };
+}
diff --git a/tests/src/lib.rs b/tests/src/lib.rs
index 614baa969..473617d18 100644
--- a/tests/src/lib.rs
+++ b/tests/src/lib.rs
@@ -56,6 +56,9 @@ mod submessage_without_package;
 #[cfg(test)]
 mod type_names;
 
+#[cfg(test)]
+mod boxed_field;
+
 mod test_enum_named_option_value {
     include!(concat!(env!("OUT_DIR"), "/myenum.optionn.rs"));
 }
@@ -140,10 +143,6 @@ pub mod invalid {
     }
 }
 
-pub mod boxed_field {
-    include!(concat!(env!("OUT_DIR"), "/boxed_field.rs"));
-}
-
 pub mod default_string_escape {
     include!(concat!(env!("OUT_DIR"), "/default_string_escape.rs"));
 }