diff --git a/internal/archiver/testing.go b/internal/archiver/testing.go
index 873e9ab5d..d8ad0a9e7 100644
--- a/internal/archiver/testing.go
+++ b/internal/archiver/testing.go
@@ -234,6 +234,7 @@ func TestEnsureFileContent(ctx context.Context, t testing.TB, repo restic.Reposi
 			return
 		}
 
+		copy(content[pos:pos+len(part)], part)
 		pos += len(part)
 	}