diff --git a/block/blkdebug.c b/block/blkdebug.c
index 3c088934db..a562e2e32f 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -429,6 +429,13 @@ blkdebug_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
     BDRVBlkdebugState *s = bs->opaque;
     BlkdebugRule *rule = NULL;
 
+    /* Sanity check block layer guarantees */
+    assert(QEMU_IS_ALIGNED(offset, bs->bl.request_alignment));
+    assert(QEMU_IS_ALIGNED(bytes, bs->bl.request_alignment));
+    if (bs->bl.max_transfer) {
+        assert(bytes <= bs->bl.max_transfer);
+    }
+
     QSIMPLEQ_FOREACH(rule, &s->active_rules, active_next) {
         uint64_t inject_offset = rule->options.inject.offset;
 
@@ -453,6 +460,13 @@ blkdebug_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
     BDRVBlkdebugState *s = bs->opaque;
     BlkdebugRule *rule = NULL;
 
+    /* Sanity check block layer guarantees */
+    assert(QEMU_IS_ALIGNED(offset, bs->bl.request_alignment));
+    assert(QEMU_IS_ALIGNED(bytes, bs->bl.request_alignment));
+    if (bs->bl.max_transfer) {
+        assert(bytes <= bs->bl.max_transfer);
+    }
+
     QSIMPLEQ_FOREACH(rule, &s->active_rules, active_next) {
         uint64_t inject_offset = rule->options.inject.offset;