diff --git a/nova/objects/numa.py b/nova/objects/numa.py
index 4ce040154c08..8c841b7a2d7d 100644
--- a/nova/objects/numa.py
+++ b/nova/objects/numa.py
@@ -96,6 +96,12 @@ class NUMACell(base.NovaObject):
         self.pinned_cpus -= cpus
 
     def pin_cpus_with_siblings(self, cpus):
+        # NOTE(snikitin): Empty siblings list means that HyperThreading is
+        # disabled on the NUMA cell and we must pin CPUs like normal CPUs.
+        if not self.siblings:
+            self.pin_cpus(cpus)
+            return
+
         pin_siblings = set()
         for sib in self.siblings:
             if cpus & sib:
@@ -103,6 +109,12 @@ class NUMACell(base.NovaObject):
         self.pin_cpus(pin_siblings)
 
     def unpin_cpus_with_siblings(self, cpus):
+        # NOTE(snikitin): Empty siblings list means that HyperThreading is
+        # disabled on the NUMA cell and we must unpin CPUs like normal CPUs.
+        if not self.siblings:
+            self.unpin_cpus(cpus)
+            return
+
         pin_siblings = set()
         for sib in self.siblings:
             if cpus & sib:
diff --git a/nova/tests/unit/objects/test_numa.py b/nova/tests/unit/objects/test_numa.py
index 1e1bf76e7148..6eda93b61111 100644
--- a/nova/tests/unit/objects/test_numa.py
+++ b/nova/tests/unit/objects/test_numa.py
@@ -124,6 +124,25 @@ class _TestNUMA(object):
         numacell.unpin_cpus_with_siblings(set([4]))
         self.assertEqual(set([1, 2, 3, 4]), numacell.free_cpus)
 
+    def test_pinning_with_siblings_with_empty_siblings_list(self):
+        numacell = objects.NUMACell(id=0, cpuset=set([1, 2, 3, 4]), memory=512,
+                                    cpu_usage=0, memory_usage=256,
+                                    pinned_cpus=set([]),
+                                    siblings=[],
+                                    mempages=[])
+
+        numacell.pin_cpus_with_siblings(set([1, 2]))
+        self.assertEqual(set([1, 2]), numacell.pinned_cpus)
+        numacell.unpin_cpus_with_siblings(set([1]))
+        self.assertEqual(set([2]), numacell.pinned_cpus)
+        self.assertRaises(exception.CPUUnpinningInvalid,
+                          numacell.unpin_cpus_with_siblings,
+                          set([1]))
+        self.assertRaises(exception.CPUPinningInvalid,
+                          numacell.pin_cpus_with_siblings,
+                          set([2]))
+        self.assertEqual(set([2]), numacell.pinned_cpus)
+
     def test_pages_topology_wipe(self):
         pages_topology = objects.NUMAPagesTopology(
             size_kb=2048, total=1024, used=512)
diff --git a/nova/tests/unit/virt/test_hardware.py b/nova/tests/unit/virt/test_hardware.py
index 78c5ec1cbbf9..003859319367 100644
--- a/nova/tests/unit/virt/test_hardware.py
+++ b/nova/tests/unit/virt/test_hardware.py
@@ -2765,6 +2765,48 @@ class CPUPinningTestCase(test.NoDBTestCase, _CPUPinningTestCaseBase):
         self.assertEqual(set([]), new_cell.cells[0].pinned_cpus)
         self.assertEqual(new_cell.cells[0].cpu_usage, 0)
 
+    def test_host_usage_from_instances_isolated_without_siblings(self):
+        host_pin = objects.NUMATopology(
+                cells=[objects.NUMACell(id=0, cpuset=set([0, 1, 2, 3]),
+                                        memory=4096, cpu_usage=0,
+                                        memory_usage=0,
+                                        siblings=[],
+                                        mempages=[], pinned_cpus=set([]))])
+        inst_pin = objects.InstanceNUMATopology(
+            cells=[objects.InstanceNUMACell(
+                cpuset=set([0, 1, 2]), memory=2048, id=0,
+                cpu_pinning={0: 0, 1: 1, 2: 2},
+                cpu_policy=fields.CPUAllocationPolicy.DEDICATED,
+                cpu_thread_policy=fields.CPUThreadAllocationPolicy.ISOLATE
+            )])
+
+        new_cell = hw.numa_usage_from_instances(host_pin, [inst_pin])
+        self.assertEqual(inst_pin.cells[0].cpuset,
+                         new_cell.cells[0].pinned_cpus)
+        self.assertEqual(new_cell.cells[0].cpu_usage, 3)
+
+    def test_host_usage_from_instances_isolated_without_siblings_free(self):
+        host_pin = objects.NUMATopology(
+                cells=[objects.NUMACell(id=0, cpuset=set([0, 1, 2, 3]),
+                                        memory=4096, cpu_usage=4,
+                                        memory_usage=0,
+                                        siblings=[],
+                                        mempages=[],
+                                        pinned_cpus=set([0, 1, 2, 3]))])
+        inst_pin = objects.InstanceNUMATopology(
+                cells=[objects.InstanceNUMACell(
+                    cpuset=set([0, 1, 3]), memory=2048, id=0,
+                    cpu_pinning={0: 0, 1: 1, 2: 2},
+                    cpu_policy=fields.CPUAllocationPolicy.DEDICATED,
+                    cpu_thread_policy=fields.CPUThreadAllocationPolicy.ISOLATE
+                )])
+
+        new_cell = hw.numa_usage_from_instances(host_pin,
+                                                [inst_pin],
+                                                free=True)
+        self.assertEqual(set([3]), new_cell.cells[0].pinned_cpus)
+        self.assertEqual(new_cell.cells[0].cpu_usage, 1)
+
 
 class CPURealtimeTestCase(test.NoDBTestCase):
     def test_success_flavor(self):