diff --git a/builder/proxmox/config.go b/builder/proxmox/config.go
index e35c408f3..8b60c509f 100644
--- a/builder/proxmox/config.go
+++ b/builder/proxmox/config.go
@@ -61,7 +61,7 @@ type diskConfig struct {
 	Type            string `mapstructure:"type"`
 	StoragePool     string `mapstructure:"storage_pool"`
 	StoragePoolType string `mapstructure:"storage_pool_type"`
-	Size            string `mapstructure:"size"`
+	Size            string `mapstructure:"disk_size"`
 	CacheMode       string `mapstructure:"cache_mode"`
 	DiskFormat      string `mapstructure:"format"`
 }
diff --git a/builder/proxmox/config_test.go b/builder/proxmox/config_test.go
index a7496dddd..e04f4a0d5 100644
--- a/builder/proxmox/config_test.go
+++ b/builder/proxmox/config_test.go
@@ -52,7 +52,7 @@ func TestBasicExampleFromDocsIsValid(t *testing.T) {
       "disks": [
         {
           "type": "scsi",
-          "size": "5G",
+          "disk_size": "5G",
           "storage_pool": "local-lvm",
           "storage_pool_type": "lvm"
         }