diff --git a/internal/osbuild2/files_input.go b/internal/osbuild2/files_input.go
index bb2e0e70b..93e545972 100644
--- a/internal/osbuild2/files_input.go
+++ b/internal/osbuild2/files_input.go
@@ -24,6 +24,9 @@ func NewFilesInputs(references FilesInputReferences) *FilesInputs {
 // inputs accepted by the XZ stage
 func (FilesInputs) isXzStageInputs() {}
 
+// inputs accepted by the Copy stage
+func (FilesInputs) isCopyStageInputs() {}
+
 // SPECIFIC INPUT STRUCTURE
 
 type FilesInput struct {