diff --git a/search_knn.go b/search_knn.go
index 025c7ab1b..bd38994be 100644
--- a/search_knn.go
+++ b/search_knn.go
@@ -90,7 +90,7 @@ type KNNRequest struct {
 
 	// Filter query to use with kNN pre-filtering.
 	// Supports pre-filtering with all existing types of query clauses.
-	FilterQuery query.Query `JSON:"filter,omitempty"`
+	FilterQuery interface{} `JSON:"filter,omitempty"`
 }
 
 func (r *SearchRequest) AddKNN(field string, vector []float32, k int64, boost float64) {
@@ -104,7 +104,7 @@ func (r *SearchRequest) AddKNN(field string, vector []float32, k int64, boost fl
 }
 
 func (r *SearchRequest) AddKNNWithFilter(field string, vector []float32, k int64,
-	boost float64, filterQuery query.Query) {
+	boost float64, filterQuery interface{}) {
 	b := query.Boost(boost)
 	r.KNN = append(r.KNN, &KNNRequest{
 		Field:       field,
@@ -275,7 +275,7 @@ func createKNNQuery(req *SearchRequest, eligibleDocsMap map[int][]index.IndexInt
 			knnQuery.SetBoost(knn.Boost.Value())
 			knnQuery.SetParams(knn.Params)
 			if len(eligibleDocsMap[i]) > 0 {
-				knnQuery.SetFilterQuery(knn.FilterQuery)
+				knnQuery.SetFilterQuery(knn.FilterQuery.(query.Query))
 				filterResults, exists := eligibleDocsMap[i]
 				if exists {
 					knnQuery.SetFilterResults(filterResults)
@@ -389,7 +389,7 @@ func (i *indexImpl) runKnnCollector(ctx context.Context, req *SearchRequest, rea
 		}
 
 		// Applies to all supported types of queries.
-		filterSearcher, _ := filterQ.Searcher(ctx, reader, i.m, search.SearcherOptions{
+		filterSearcher, _ := filterQ.(query.Query).Searcher(ctx, reader, i.m, search.SearcherOptions{
 			Score: "none", // just want eligible hits --> don't compute scores if not needed
 		})
 		// Using the index doc count to determine collector size since we do not