diff --git a/tpe/sampler.go b/tpe/sampler.go
index cf3da4fc..1530e3a1 100644
--- a/tpe/sampler.go
+++ b/tpe/sampler.go
@@ -542,6 +542,9 @@ func getObservationPairs(study *goptuna.Study, paramName string) ([]float64, [][
 	values := make([]float64, 0, len(trials))
 	scores := make([][2]float64, 0, len(trials))
 	for _, trial := range trials {
+		if trial.State != goptuna.TrialStateComplete && trial.State != goptuna.TrialStatePruned {
+			continue
+		}
 		ir, ok := trial.InternalParams[paramName]
 		if !ok {
 			continue
@@ -552,7 +555,7 @@ func getObservationPairs(study *goptuna.Study, paramName string) ([]float64, [][
 		if trial.State == goptuna.TrialStateComplete {
 			score0 = math.Inf(-1)
 			score1 = sign * trial.Value
-		} else if trial.State == goptuna.TrialStatePruned {
+		} else {
 			if len(trial.IntermediateValues) > 0 {
 				var step int
 				var intermediateValue float64
@@ -569,8 +572,6 @@ func getObservationPairs(study *goptuna.Study, paramName string) ([]float64, [][
 				score0 = math.Inf(1)
 				score1 = 0.0
 			}
-		} else {
-			continue
 		}
 		values = append(values, paramValue)
 		scores = append(scores, [2]float64{score0, score1})