diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 04c8df7232..c467092bcc 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -3264,6 +3264,9 @@ qemuBuildNetworkDriveURI(virStorageSourcePtr src,
 
         case VIR_STORAGE_NET_PROTOCOL_LAST:
         case VIR_STORAGE_NET_PROTOCOL_NONE:
+            virReportError(VIR_ERR_INTERNAL_ERROR,
+                           _("Unexpected network protocol '%s'"),
+                           virStorageNetProtocolTypeToString(src->protocol));
             goto cleanup;
     }