diff --git a/README.rst b/README.rst
index 6d9c848..38b1b7b 100644
--- a/README.rst
+++ b/README.rst
@@ -265,6 +265,7 @@
         - hosts_with_ssd
         security_group: true
         resume_guests_state_on_host_boot: False
+        preallocate_images: space  # Default is 'none'
         my_ip: 10.1.0.16
         bind:
           vnc_address: 172.20.0.100
diff --git a/nova/files/pike/nova-compute.conf.Debian b/nova/files/pike/nova-compute.conf.Debian
index 5427ce6..4c51e6f 100644
--- a/nova/files/pike/nova-compute.conf.Debian
+++ b/nova/files/pike/nova-compute.conf.Debian
@@ -374,6 +374,9 @@
 #  (string value)
 # Allowed values: none, space
 #preallocate_images=none
+{%- if compute.preallocate_images is defined %}
+preallocate_images = {{ compute.preallocate_images }}
+{%- endif %}
 
 #
 # Enable use of copy-on-write (cow) images.
diff --git a/nova/files/queens/nova-compute.conf.Debian b/nova/files/queens/nova-compute.conf.Debian
index 98611a2..afaafb7 100644
--- a/nova/files/queens/nova-compute.conf.Debian
+++ b/nova/files/queens/nova-compute.conf.Debian
@@ -376,6 +376,9 @@
 # none - <No description provided>
 # space - <No description provided>
 #preallocate_images = none
+{%- if compute.preallocate_images is defined %}
+preallocate_images = {{ compute.preallocate_images }}
+{%- endif %}
 
 #
 # Enable use of copy-on-write (cow) images.
diff --git a/tests/pillar/compute_cluster.sls b/tests/pillar/compute_cluster.sls
index 28ded0c..4bbcfba 100644
--- a/tests/pillar/compute_cluster.sls
+++ b/tests/pillar/compute_cluster.sls
@@ -13,6 +13,7 @@
     report_interval: 60
     vnc_keymap: en-gb
     resume_guests_state_on_host_boot: True
+    preallocate_images: space
     bind:
       vnc_address: 127.0.0.1
       vnc_port: 6080
diff --git a/tests/pillar/compute_single.sls b/tests/pillar/compute_single.sls
index 08250ba..211a60e 100644
--- a/tests/pillar/compute_single.sls
+++ b/tests/pillar/compute_single.sls
@@ -7,6 +7,7 @@
     vncproxy_url: openstack:6080
     vnc_keymap: en-gb
     resume_guests_state_on_host_boot: False
+    preallocate_images: space
     cpu_mode: custom
     libvirt:
       cpu_model: IvyBridge
diff --git a/tests/pillar/compute_single_config_drive_options.sls b/tests/pillar/compute_single_config_drive_options.sls
index 75840b7..a3c03da 100644
--- a/tests/pillar/compute_single_config_drive_options.sls
+++ b/tests/pillar/compute_single_config_drive_options.sls
@@ -7,6 +7,7 @@
     vncproxy_url: openstack:6080
     vnc_keymap: en-gb
     resume_guests_state_on_host_boot: False
+    preallocate_images: space
     bind:
       vnc_address: 127.0.0.1
       vnc_port: 6080
@@ -60,4 +61,4 @@
     config_drive:
       cdrom: True
       format: iso9660
-      inject_password: True
\ No newline at end of file
+      inject_password: True