diff --git a/pkg/scheduler/core/extender.go b/pkg/scheduler/core/extender.go
index 5f1c306b5008..b5a478a6caab 100644
--- a/pkg/scheduler/core/extender.go
+++ b/pkg/scheduler/core/extender.go
@@ -253,8 +253,8 @@ func convertToNodeNameToVictims(
 }
 
 // Filter based on extender implemented predicate functions. The filtered list is
-// expected to be a subset of the supplied list. failedNodesMap optionally contains
-// the list of failed nodes and failure reasons.
+// expected to be a subset of the supplied list; otherwise the function returns an error.
+// failedNodesMap optionally contains the list of failed nodes and failure reasons.
 func (h *HTTPExtender) Filter(
 	pod *v1.Pod,
 	nodes []*v1.Node, nodeNameToInfo map[string]*schedulernodeinfo.NodeInfo,
@@ -298,14 +298,20 @@ func (h *HTTPExtender) Filter(
 	}
 
 	if h.nodeCacheCapable && result.NodeNames != nil {
-		nodeResult = make([]*v1.Node, 0, len(*result.NodeNames))
-		for i := range *result.NodeNames {
-			nodeResult = append(nodeResult, nodeNameToInfo[(*result.NodeNames)[i]].Node())
+		nodeResult = make([]*v1.Node, len(*result.NodeNames))
+		for i, nodeName := range *result.NodeNames {
+			if node, ok := nodeNameToInfo[nodeName]; ok {
+				nodeResult[i] = node.Node()
+			} else {
+				return nil, nil, fmt.Errorf(
+					"extender %q claims a filtered node %q which is not found in nodeNameToInfo map",
+					h.extenderURL, nodeName)
+			}
 		}
 	} else if result.Nodes != nil {
-		nodeResult = make([]*v1.Node, 0, len(result.Nodes.Items))
+		nodeResult = make([]*v1.Node, len(result.Nodes.Items))
 		for i := range result.Nodes.Items {
-			nodeResult = append(nodeResult, &result.Nodes.Items[i])
+			nodeResult[i] = &result.Nodes.Items[i]
 		}
 	}
 
diff --git a/pkg/scheduler/scheduler.go b/pkg/scheduler/scheduler.go
index 8aa675124973..3daf44ed6746 100644
--- a/pkg/scheduler/scheduler.go
+++ b/pkg/scheduler/scheduler.go
@@ -304,7 +304,7 @@ func (sched *Scheduler) preempt(preemptor *v1.Pod, scheduleErr error) (string, e
 
 	node, victims, nominatedPodsToClear, err := sched.config.Algorithm.Preempt(preemptor, sched.config.NodeLister, scheduleErr)
 	if err != nil {
-		klog.Errorf("Error preempting victims to make room for %v/%v.", preemptor.Namespace, preemptor.Name)
+		klog.Errorf("Error preempting victims to make room for %v/%v: %v", preemptor.Namespace, preemptor.Name, err)
 		return "", err
 	}
 	var nodeName = ""