diff --git a/build/soong/build_files.go b/build/soong/build_files.go
index 383a282..ed92f1a 100644
--- a/build/soong/build_files.go
+++ b/build/soong/build_files.go
@@ -80,7 +80,7 @@
 		return paths, nil
 	}
 
-	return nil, fmt.Errorf("unknown tag %q. Supported tags are: %q", tag, strings.Join(android.SortedStringKeys(b.srcs), " "))
+	return nil, fmt.Errorf("unknown tag %q. Supported tags are: %q", tag, strings.Join(android.SortedKeys(b.srcs), " "))
 }
 
 var _ android.OutputFileProducer = (*buildFiles)(nil)