diff --git a/packages/grafana-data/src/dataframe/StreamingDataFrame.test.ts b/packages/grafana-data/src/dataframe/StreamingDataFrame.test.ts
index 19b9c4a18f2..99abb85cc01 100644
--- a/packages/grafana-data/src/dataframe/StreamingDataFrame.test.ts
+++ b/packages/grafana-data/src/dataframe/StreamingDataFrame.test.ts
@@ -1,3 +1,4 @@
+import { reduceField, ReducerID } from '..';
 import { DataFrame, FieldType } from '../types/dataFrame';
 import { DataFrameJSON } from './DataFrameJSON';
 import { StreamingDataFrame } from './StreamingDataFrame';
@@ -200,10 +201,14 @@ describe('Streaming JSON', () => {
         maxLength: 5,
       }
     );
+    let val = reduceField({ field: stream.fields[0], reducers: [ReducerID.lastNotNull] })[ReducerID.lastNotNull];
+    expect(val).toEqual(100);
     expect(stream.length).toEqual(1);
     stream.push({
       data: { values: [[200]] },
     });
+    val = reduceField({ field: stream.fields[0], reducers: [ReducerID.lastNotNull] })[ReducerID.lastNotNull];
+    expect(val).toEqual(200);
     expect(stream.length).toEqual(2);
 
     const copy = ({ ...stream } as any) as DataFrame;
diff --git a/packages/grafana-data/src/dataframe/StreamingDataFrame.ts b/packages/grafana-data/src/dataframe/StreamingDataFrame.ts
index f87457c2111..94a19173321 100644
--- a/packages/grafana-data/src/dataframe/StreamingDataFrame.ts
+++ b/packages/grafana-data/src/dataframe/StreamingDataFrame.ts
@@ -178,7 +178,11 @@ export class StreamingDataFrame implements DataFrame {
       let appended = circPush(curValues, values, this.options.maxLength, this.timeFieldIndex, this.options.maxDelta);
 
       appended.forEach((v, i) => {
-        this.fields[i].values.buffer = v;
+        const { state, values } = this.fields[i];
+        values.buffer = v;
+        if (state) {
+          state.calcs = undefined;
+        }
       });
 
       // Update the frame length
diff --git a/packages/grafana-data/src/transformations/fieldReducer.ts b/packages/grafana-data/src/transformations/fieldReducer.ts
index e23fdad4cb8..7e2d7cc5f49 100644
--- a/packages/grafana-data/src/transformations/fieldReducer.ts
+++ b/packages/grafana-data/src/transformations/fieldReducer.ts
@@ -46,6 +46,8 @@ interface ReduceFieldOptions {
 
 /**
  * @returns an object with a key for each selected stat
+ * NOTE: This will also modify the 'field.state' object,
+ * leaving values in a cache until cleared.
  */
 export function reduceField(options: ReduceFieldOptions): FieldCalcs {
   const { field, reducers } = options;