diff --git a/crates/ailang-core/src/primitives.rs b/crates/ailang-core/src/primitives.rs
index d0cf912..1f00aad 100644
--- a/crates/ailang-core/src/primitives.rs
+++ b/crates/ailang-core/src/primitives.rs
@@ -49,7 +49,10 @@ mod tests {
                 "lockstep violation for {name:?}"
             );
         }
-        // Float is a primitive (Floats milestone, iter 1).
+        // The loop's assert_eq! passes vacuously when both functions
+        // return `false`/`None` for a name; the explicit assertions
+        // below catch the case where a primitive is silently removed
+        // from both functions but stays in the loop list.
         assert!(is_primitive_name("Float"), "Float must be a primitive");
         assert_eq!(
             primitive_surface_name("Float"),