diff --git a/federationapi/federationapi_test.go b/federationapi/federationapi_test.go
index 7e091d97b..79f4b3f21 100644
--- a/federationapi/federationapi_test.go
+++ b/federationapi/federationapi_test.go
@@ -370,8 +370,6 @@ func TestRoomsV3URLEscapeDoNot404(t *testing.T) {
 }
 
 func TestNotaryServer(t *testing.T) {
-
-	// Start a server we are going to request keys from
 	testCases := []struct {
 		name          string
 		httpBody      string
@@ -381,11 +379,10 @@ func TestNotaryServer(t *testing.T) {
 		{
 			name: "empty httpBody",
 			validateFunc: func(t *testing.T, resp util.JSONResponse) {
-				want := util.JSONResponse{
-					Code: http.StatusBadRequest,
-					JSON: spec.BadJSON("The request body could not be decoded into valid JSON. unexpected end of JSON input"),
-				}
-				assert.Equal(t, want, resp)
+				assert.Equal(t, http.StatusBadRequest, resp.Code)
+				nk, ok := resp.JSON.(spec.MatrixError)
+				assert.True(t, ok)
+				assert.Equal(t, spec.ErrorBadJSON, nk.ErrCode)
 			},
 		},
 		{
@@ -394,13 +391,13 @@ func TestNotaryServer(t *testing.T) {
 			validateFunc: func(t *testing.T, resp util.JSONResponse) {
 				want := util.JSONResponse{
 					Code: http.StatusOK,
-					JSON: routing.NotaryKeysResponse{},
+					JSON: routing.NotaryKeysResponse{ServerKeys: []json.RawMessage{}},
 				}
 				assert.Equal(t, want, resp)
 			},
 		},
 		{
-			name:     "request all keys",
+			name:     "request all keys using an empty criteria",
 			httpBody: `{"server_keys":{"servera":{}}}`,
 			validateFunc: func(t *testing.T, resp util.JSONResponse) {
 				assert.Equal(t, http.StatusOK, resp.Code)
@@ -410,6 +407,17 @@ func TestNotaryServer(t *testing.T) {
 				assert.True(t, gjson.GetBytes(nk.ServerKeys[0], "verify_keys.ed25519:someID").Exists())
 			},
 		},
+		{
+			name:     "request all keys using null as the criteria",
+			httpBody: `{"server_keys":{"servera":null}}`,
+			validateFunc: func(t *testing.T, resp util.JSONResponse) {
+				assert.Equal(t, http.StatusOK, resp.Code)
+				nk, ok := resp.JSON.(routing.NotaryKeysResponse)
+				assert.True(t, ok)
+				assert.Equal(t, "servera", gjson.GetBytes(nk.ServerKeys[0], "server_name").Str)
+				assert.True(t, gjson.GetBytes(nk.ServerKeys[0], "verify_keys.ed25519:someID").Exists())
+			},
+		},
 		{
 			name:     "request specific key",
 			httpBody: `{"server_keys":{"servera":{"ed25519:someID":{}}}}`,
diff --git a/federationapi/routing/keys.go b/federationapi/routing/keys.go
index fea69bd05..38a88e4b1 100644
--- a/federationapi/routing/keys.go
+++ b/federationapi/routing/keys.go
@@ -221,7 +221,9 @@ func NotaryKeys(
 		}
 	}
 
-	response := NotaryKeysResponse{}
+	response := NotaryKeysResponse{
+		ServerKeys: []json.RawMessage{},
+	}
 
 	for serverName, kidToCriteria := range req.ServerKeys {
 		var keyList []gomatrixserverlib.ServerKeys