diff --git a/block.c b/block.c
index d36eb75be96a..d4939b49bf05 100644
--- a/block.c
+++ b/block.c
@@ -1526,6 +1526,13 @@ static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
         if (!bs) {
             return -ENODEV;
         }
+
+        if (bs->throttle_state) {
+            error_setg(errp, "Cannot reference an existing block device for "
+                       "which I/O throttling is enabled");
+            return -EINVAL;
+        }
+
         bdrv_ref(bs);
         *pbs = bs;
         return 0;
diff --git a/block/crypto.c b/block/crypto.c
index be3498581c55..1903e84fbd85 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -196,6 +196,7 @@ block_crypto_open_opts_init(QCryptoBlockFormat format,
     OptsVisitor *ov;
     QCryptoBlockOpenOptions *ret = NULL;
     Error *local_err = NULL;
+    Error *end_err = NULL;
 
     ret = g_new0(QCryptoBlockOpenOptions, 1);
     ret->format = format;
@@ -218,10 +219,9 @@ block_crypto_open_opts_init(QCryptoBlockFormat format,
         error_setg(&local_err, "Unsupported block format %d", format);
         break;
     }
-    error_propagate(errp, local_err);
-    local_err = NULL;
 
-    visit_end_struct(opts_get_visitor(ov), &local_err);
+    visit_end_struct(opts_get_visitor(ov), &end_err);
+    error_propagate(&local_err, end_err);
 
  out:
     if (local_err) {
@@ -242,6 +242,7 @@ block_crypto_create_opts_init(QCryptoBlockFormat format,
     OptsVisitor *ov;
     QCryptoBlockCreateOptions *ret = NULL;
     Error *local_err = NULL;
+    Error *end_err = NULL;
 
     ret = g_new0(QCryptoBlockCreateOptions, 1);
     ret->format = format;
@@ -264,10 +265,9 @@ block_crypto_create_opts_init(QCryptoBlockFormat format,
         error_setg(&local_err, "Unsupported block format %d", format);
         break;
     }
-    error_propagate(errp, local_err);
-    local_err = NULL;
 
-    visit_end_struct(opts_get_visitor(ov), &local_err);
+    visit_end_struct(opts_get_visitor(ov), &end_err);
+    error_propagate(&local_err, end_err);
 
  out:
     if (local_err) {
diff --git a/blockdev.c b/blockdev.c
index e50e8eabd094..f1f520a2653b 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2661,6 +2661,13 @@ void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd,
         goto out;
     }
 
+    /* The BlockBackend must be the only parent */
+    assert(QLIST_FIRST(&bs->parents));
+    if (QLIST_NEXT(QLIST_FIRST(&bs->parents), next_parent)) {
+        error_setg(errp, "Cannot throttle device with multiple parents");
+        goto out;
+    }
+
     throttle_config_init(&cfg);
     cfg.buckets[THROTTLE_BPS_TOTAL].avg = bps;
     cfg.buckets[THROTTLE_BPS_READ].avg  = bps_rd;
@@ -4027,6 +4034,11 @@ void qmp_x_blockdev_del(bool has_id, const char *id,
             error_setg(errp, "Cannot find block backend %s", id);
             return;
         }
+        if (blk_legacy_dinfo(blk)) {
+            error_setg(errp, "Deleting block backend added with drive-add"
+                       " is not supported");
+            return;
+        }
         if (blk_get_refcnt(blk) > 1) {
             error_setg(errp, "Block backend %s is in use", id);
             return;
diff --git a/tests/qemu-iotests/149 b/tests/qemu-iotests/149
index bb5811d93b44..52e23d2946e2 100755
--- a/tests/qemu-iotests/149
+++ b/tests/qemu-iotests/149
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 #
 # Copyright (C) 2016 Red Hat, Inc.
 #