diff --git a/lib/searchkick/query.rb b/lib/searchkick/query.rb
index 22d782c6..ef9caccc 100644
--- a/lib/searchkick/query.rb
+++ b/lib/searchkick/query.rb
@@ -532,23 +532,20 @@ def prepare
           raise ArgumentError, "Hybrid search not supported yet"
         end
 
-        if options[:where]
-          raise ArgumentError, "KNN search with where not supported yet"
-        end
-
         if options[:knn].size != 1
           raise ArgumentError, "Invalid knn option"
         end
 
         k = per_page + offset
+        filter = payload.delete(:query)
 
         if Searchkick.opensearch?
-          payload[:query].delete(:match_all)
-          payload[:query][:knn] = {}
+          payload[:query] = {knn: {}}
           options[:knn].each do |field, vector|
             payload[:query][:knn][field.to_sym] = {
               vector: vector,
-              k: k
+              k: k,
+              filter: filter
             }
           end
         else
@@ -556,7 +553,8 @@ def prepare
             payload[:knn] = {
               field: field,
               k: k,
-              query_vector: vector
+              query_vector: vector,
+              filter: filter
             }
           end
         end
diff --git a/test/knn_test.rb b/test/knn_test.rb
index 55afc9e5..6956d4bb 100644
--- a/test/knn_test.rb
+++ b/test/knn_test.rb
@@ -6,13 +6,17 @@ def setup
     super
   end
 
-  def test_works
+  def test_basic
     store [{name: "A", embedding: [1, 2, 3]}, {name: "B", embedding: [-1, -2, -3]}]
     assert_order "*", ["A", "B"], knn: {embedding: [1, 2, 3]}
 
-    expected = Searchkick.opensearch? ? [1, 0] : [2, 1]
     scores = Product.search(knn: {embedding: [1, 2, 3]}).hits.map { |v| v["_score"] }
-    assert_in_delta expected[0], scores[0]
-    assert_in_delta expected[1], scores[1]
+    assert_in_delta 1, scores[0]
+    assert_in_delta 0, scores[1]
+  end
+
+  def test_where
+    store [{name: "A", store_id: 1, embedding: [1, 2, 3]}, {name: "B", store_id: 2, embedding: [-1, -2, -3]}]
+    assert_order "*", ["A"], knn: {embedding: [1, 2, 3]}, where: {store_id: 1}
   end
 end