diff --git a/src/gallium/drivers/iris/iris_bufmgr.c b/src/gallium/drivers/iris/iris_bufmgr.c
index e04712a2540..897f333346e 100644
--- a/src/gallium/drivers/iris/iris_bufmgr.c
+++ b/src/gallium/drivers/iris/iris_bufmgr.c
@@ -997,6 +997,12 @@ alloc_fresh_bo(struct iris_bufmgr *bufmgr, uint64_t bo_size, unsigned flags)
          .extensions = (uintptr_t)&ext_regions,
       };
 
+      /* TODO: Add I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS to create.flags
+       * for IRIS_HEAP_DEVICE_LOCAL_PREFERRED when small BAR uapi is
+       * stabilized.
+       */
+      assert(bufmgr->all_vram_mappable);
+
       /* It should be safe to use GEM_CREATE_EXT without checking, since we are
        * in the side of the branch where discrete memory is available. So we
        * can assume GEM_CREATE_EXT is supported already.