diff --git a/.changelog/3826.txt b/.changelog/3826.txt
new file mode 100644
index 00000000000..98b90672536
--- /dev/null
+++ b/.changelog/3826.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+monitoring: fixed validation rules for `google_monitoring_slo` `windows_based_sli.metric_sum_in_range.max` field
+```
diff --git a/google/resource_monitoring_slo.go b/google/resource_monitoring_slo.go
index e531e7bfa48..2e832e17841 100644
--- a/google/resource_monitoring_slo.go
+++ b/google/resource_monitoring_slo.go
@@ -621,7 +621,7 @@ just one of min or max. Summed value 'X' should satisfy
 													Description: `max value for the range (inclusive). If not given,
 will be set to "infinity", defining an open range
 ">= range.min"`,
-													AtLeastOneOf: []string{"windows_based_sli.0.metric_mean_in_range.0.range.0.min", "windows_based_sli.0.metric_mean_in_range.0.range.0.max"},
+													AtLeastOneOf: []string{"windows_based_sli.0.metric_sum_in_range.0.range.0.min", "windows_based_sli.0.metric_sum_in_range.0.range.0.max"},
 												},
 												"min": {
 													Type:     schema.TypeInt,