diff --git a/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/TimeSeriesIT.java b/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/TimeSeriesIT.java
index 63dd77b2a4474..bbf108b4ed424 100644
--- a/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/TimeSeriesIT.java
+++ b/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/TimeSeriesIT.java
@@ -103,7 +103,9 @@ public void populateIndex() {
                 "memory",
                 "type=long,time_series_metric=gauge",
                 "request_count",
-                "type=integer,time_series_metric=counter"
+                "type=integer,time_series_metric=counter",
+                "description",
+                "type=text,index=true"
             )
             .get();
         Map<String, String> hostToClusters = new HashMap<>();
@@ -145,7 +147,9 @@ public void populateIndex() {
                     "memory",
                     doc.memory.getBytes(),
                     "request_count",
-                    doc.requestCount
+                    doc.requestCount,
+                    "description",
+                    "host = " + doc.host
                 )
                 .get();
         }
@@ -200,6 +204,23 @@ public void testImplicitAggregate() {
         }
     }
 
+    public void testGroupByTextField() {
+        List<String> sortedGroups = docs.stream().map(d -> d.host).distinct().sorted().toList();
+        client().admin().indices().prepareRefresh("hosts").get();
+        for (String fn : List.of("count", "count_distinct", "sum", "avg", "max", "min")) {
+            try (var resp = run("TS hosts | STATS " + fn + "(cpu) BY description | SORT description | LIMIT 1")) {
+                List<List<Object>> rows = EsqlTestUtils.getValuesList(resp);
+                assertThat(rows, hasSize(1));
+                assertThat(rows.get(0).get(1), equalTo("host = " + sortedGroups.get(0)));
+            }
+        }
+        try (var resp = run("TS hosts | STATS sum(rate(request_count)) BY description | SORT description | LIMIT 1")) {
+            List<List<Object>> rows = EsqlTestUtils.getValuesList(resp);
+            assertThat(rows, hasSize(1));
+            assertThat(rows.get(0).get(1), equalTo("host = " + sortedGroups.get(0)));
+        }
+    }
+
     public void testRateWithoutGrouping() {
         record RateKey(String cluster, String host) {
 
diff --git a/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/PostOptimizationPhasePlanVerifier.java b/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/PostOptimizationPhasePlanVerifier.java
index e187264b2432f..6570dc330ffd2 100644
--- a/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/PostOptimizationPhasePlanVerifier.java
+++ b/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/PostOptimizationPhasePlanVerifier.java
@@ -8,9 +8,13 @@
 package org.elasticsearch.xpack.esql.optimizer;
 
 import org.elasticsearch.xpack.esql.common.Failures;
+import org.elasticsearch.xpack.esql.core.expression.Alias;
 import org.elasticsearch.xpack.esql.core.expression.Attribute;
+import org.elasticsearch.xpack.esql.core.type.DataType;
+import org.elasticsearch.xpack.esql.expression.function.aggregate.Values;
 import org.elasticsearch.xpack.esql.optimizer.rules.physical.ProjectAwayColumns;
 import org.elasticsearch.xpack.esql.plan.QueryPlan;
+import org.elasticsearch.xpack.esql.plan.logical.TimeSeriesAggregate;
 import org.elasticsearch.xpack.esql.plan.physical.EsQueryExec;
 
 import java.util.List;
@@ -72,7 +76,13 @@ private static void verifyOutputNotChanged(QueryPlan<?> optimizedPlan, List<Attr
             // We perform an optimizer run on every fragment. LookupJoinExec also contains such a fragment,
             // and currently it only contains an EsQueryExec after optimization.
             boolean hasLookupJoinExec = optimizedPlan instanceof EsQueryExec esQueryExec && esQueryExec.indexMode() == LOOKUP;
-            boolean ignoreError = hasProjectAwayColumns || hasLookupJoinExec;
+            // Time-series groupings are rewritten as VALUES, changing the output type from TEXT to KEYWORD.
+            // TODO: Grouping fields in aggregations should not have the TEXT data type.
+            boolean hasTextGroupingInTimeSeries = optimizedPlan.anyMatch(
+                a -> a instanceof TimeSeriesAggregate ts
+                    && ts.aggregates().stream().anyMatch(g -> Alias.unwrap(g) instanceof Values v && v.field().dataType() == DataType.TEXT)
+            );
+            boolean ignoreError = hasProjectAwayColumns || hasLookupJoinExec || hasTextGroupingInTimeSeries;
             if (ignoreError == false) {
                 failures.add(
                     fail(