diff --git a/src/asahi/lib/agx_usc.h b/src/asahi/lib/agx_usc.h
index 8e43f571f19..18c701d68e9 100644
--- a/src/asahi/lib/agx_usc.h
+++ b/src/asahi/lib/agx_usc.h
@@ -68,6 +68,7 @@ agx_usc_uniform(struct agx_usc_builder *b, unsigned start_halfs,
                 unsigned size_halfs, uint64_t buffer)
 {
    assert((start_halfs + size_halfs) < (1 << 9) && "uniform file overflow");
+   assert(size_halfs <= 64 && "caller's responsibility to split");
 
    if (start_halfs & BITFIELD_BIT(8)) {
       agx_usc_pack(b, UNIFORM_HIGH, cfg) {