diff --git a/pkg/harvester/l10n/en-us.yaml b/pkg/harvester/l10n/en-us.yaml
index 937c2e3d..43cd7322 100644
--- a/pkg/harvester/l10n/en-us.yaml
+++ b/pkg/harvester/l10n/en-us.yaml
@@ -922,6 +922,8 @@ harvester:
     checksumTip: Validate the image using the SHA512 checksum, if specified.
     tooltip:
       imported: Created automatically by the vm-import-controller
+    errors:
+      unsupportedBackend: 'Unsupported backend type: {backend}'
 
   vmTemplate:
     label: Templates
diff --git a/pkg/harvester/models/harvesterhci.io.virtualmachineimage.js b/pkg/harvester/models/harvesterhci.io.virtualmachineimage.js
index 27f9b291..7414af70 100644
--- a/pkg/harvester/models/harvesterhci.io.virtualmachineimage.js
+++ b/pkg/harvester/models/harvesterhci.io.virtualmachineimage.js
@@ -318,8 +318,21 @@ export default class HciVmImage extends HarvesterResource {
   get uploadImage() {
     return async(file, opt = {}) => {
       const formData = new FormData();
+      const backend = this.spec?.backend || 'backingimage';
+      const backendFieldMap = {
+        cdi:          'file',
+        backingimage: 'chunk'
+      };
+      const fieldName = backendFieldMap[backend];
 
-      formData.append('chunk', file);
+      if (!fieldName) {
+        const error = this.t('harvester.image.errors.unsupportedBackend', { backend });
+
+        this.$ctx.commit('harvester-common/uploadError', { name: this.name, message: error }, { root: true });
+        throw new Error(error);
+      }
+
+      formData.append(fieldName, file);
 
       try {
         this.$ctx.commit('harvester-common/uploadStart', this.metadata.name, { root: true });