diff --git a/nova/tests/unit/virt/libvirt/test_driver.py b/nova/tests/unit/virt/libvirt/test_driver.py
index 31aef2ebd380..f3f76095d275 100644
--- a/nova/tests/unit/virt/libvirt/test_driver.py
+++ b/nova/tests/unit/virt/libvirt/test_driver.py
@@ -4932,8 +4932,7 @@ class LibvirtConnTestCase(test.NoDBTestCase,
 
         @mock.patch.object(dmcrypt, 'delete_volume')
         @mock.patch.object(conn._host, '_get_domain', return_value=dom)
-        @mock.patch.object(libvirt_driver.disk_api, 'get_allocated_disk_size')
-        def detach_encrypted_volumes(block_device_info, mock_get_alloc_size,
+        def detach_encrypted_volumes(block_device_info,
                                      mock_get_domain, mock_delete_volume):
             conn._detach_encrypted_volumes(instance, block_device_info)
 
diff --git a/nova/virt/disk/api.py b/nova/virt/disk/api.py
index eed4cdd4d814..c79ae77371a0 100644
--- a/nova/virt/disk/api.py
+++ b/nova/virt/disk/api.py
@@ -107,16 +107,6 @@ def get_disk_size(path):
     return images.qemu_img_info(path).virtual_size
 
 
-def get_allocated_disk_size(path):
-    """Get the allocated size of a disk image
-
-    :param path: Path to the disk image
-    :returns: Size (in bytes) of the given disk image as allocated on the
-              filesystem
-    """
-    return images.qemu_img_info(path).disk_size
-
-
 def extend(image, size):
     """Increase image to size.