diff --git a/phd-tests/framework/src/test_vm/config.rs b/phd-tests/framework/src/test_vm/config.rs
index 14d92fb32..2ffa98bd6 100644
--- a/phd-tests/framework/src/test_vm/config.rs
+++ b/phd-tests/framework/src/test_vm/config.rs
@@ -273,7 +273,7 @@ impl<'dr> VmConfig<'dr> {
             // name. It then derives a backend name from the disk name. Match
             // that name derivation here so PHD tests match the API as used by
             // Nexus.
-            let backend_name = format!("{}-backend", device_name);
+            let backend_name = device_name_to_backend_name(device_name);
             let device_spec = match req.interface {
                 DiskInterface::Virtio => {
                     StorageDeviceV0::VirtioDisk(VirtioDisk {
@@ -333,15 +333,21 @@ impl<'dr> VmConfig<'dr> {
     }
 }
 
+fn device_name_to_backend_name(device_name: &str) -> String {
+    format!("{}-backend", device_name)
+}
+
 async fn make_disk<'req>(
-    name: String,
+    device_name: String,
     framework: &Framework,
     req: &DiskRequest<'req>,
 ) -> anyhow::Result<Arc<dyn DiskConfig>> {
+    let backend_name = device_name_to_backend_name(&device_name);
+
     Ok(match req.backend {
         DiskBackend::File => framework
             .disk_factory
-            .create_file_backed_disk(name, &req.source)
+            .create_file_backed_disk(backend_name, &req.source)
             .await
             .with_context(|| {
                 format!("creating new file-backed disk from {:?}", req.source,)
@@ -349,7 +355,7 @@ async fn make_disk<'req>(
         DiskBackend::Crucible { min_disk_size_gib, block_size } => framework
             .disk_factory
             .create_crucible_disk(
-                name,
+                backend_name,
                 &req.source,
                 min_disk_size_gib,
                 block_size,
@@ -364,7 +370,7 @@ async fn make_disk<'req>(
             as Arc<dyn DiskConfig>,
         DiskBackend::InMemory { readonly } => framework
             .disk_factory
-            .create_in_memory_disk(name, &req.source, readonly)
+            .create_in_memory_disk(backend_name, &req.source, readonly)
             .await
             .with_context(|| {
                 format!("creating new in-memory disk from {:?}", req.source)