diff --git a/packages/grafana-data/src/transformations/transformers/concat.ts b/packages/grafana-data/src/transformations/transformers/concat.ts
index a8cb3794e20..af7eed772d4 100644
--- a/packages/grafana-data/src/transformations/transformers/concat.ts
+++ b/packages/grafana-data/src/transformations/transformers/concat.ts
@@ -89,7 +89,7 @@ export function concatenateFields(data: DataFrame[], opts: ConcatenateTransforme
       if (f.values.length === maxLength) {
         return f;
       }
-      const values = f.values;
+      const values = f.values.slice();
       values.length = maxLength;
       return {
         ...f,