diff --git a/proxmox/virtual_environment_vm_types.go b/proxmox/virtual_environment_vm_types.go
index d3a905b2..e5a3d97b 100644
--- a/proxmox/virtual_environment_vm_types.go
+++ b/proxmox/virtual_environment_vm_types.go
@@ -1075,6 +1075,10 @@ func (r CustomStorageDevice) EncodeValues(key string, v *url.Values) error {
 		values = append(values, fmt.Sprintf("mbps_wr_max=%d", *r.BurstableWriteSpeedMbps))
 	}
 
+	if r.Format != nil {
+		values = append(values, fmt.Sprintf("format=%s", *r.Format))
+	}
+
 	if r.MaxReadSpeedMbps != nil {
 		values = append(values, fmt.Sprintf("mbps_rd=%d", *r.MaxReadSpeedMbps))
 	}
diff --git a/proxmoxtf/resource_virtual_environment_vm.go b/proxmoxtf/resource_virtual_environment_vm.go
index b2fda77d..3da07410 100644
--- a/proxmoxtf/resource_virtual_environment_vm.go
+++ b/proxmoxtf/resource_virtual_environment_vm.go
@@ -2442,6 +2442,7 @@ func resourceVirtualEnvironmentVMGetDiskDeviceObjects(
 
 		block := diskEntry.(map[string]interface{})
 		datastoreID, _ := block[mkResourceVirtualEnvironmentVMDiskDatastoreID].(string)
+		fileFormat, _ := block[mkResourceVirtualEnvironmentVMDiskFileFormat].(string)
 		fileID, _ := block[mkResourceVirtualEnvironmentVMDiskFileID].(string)
 		size, _ := block[mkResourceVirtualEnvironmentVMDiskSize].(int)
 		diskInterface, _ := block[mkResourceVirtualEnvironmentVMDiskInterface].(string)
@@ -2468,6 +2469,7 @@ func resourceVirtualEnvironmentVMGetDiskDeviceObjects(
 
 		diskDevice.ID = &datastoreID
 		diskDevice.Interface = &diskInterface
+		diskDevice.Format = &fileFormat
 		diskDevice.FileID = &fileID
 		sizeString := fmt.Sprintf("%dG", size)
 		diskDevice.Size = &sizeString