diff --git a/lib/webfuse_provider/impl/json/node.c b/lib/webfuse_provider/impl/json/node.c
index 4a8c56d..4708ea9 100644
--- a/lib/webfuse_provider/impl/json/node.c
+++ b/lib/webfuse_provider/impl/json/node.c
@@ -4,39 +4,52 @@
 #include <stdlib.h>
 #include <string.h>
 
+static struct wfp_json const wfp_json_null = 
+{
+    .type = WFP_JSON_NULL,
+    .value = { .b = false }
+};
+
+bool
+wfp_impl_json_is_null(
+    struct wfp_json const * json)
+{
+    return (WFP_JSON_NULL == json->type);
+}
+
 bool
 wfp_impl_json_is_bool(
     struct wfp_json const * json)
 {
-    return ((NULL != json) &&(WFP_JSON_BOOL == json->type));
+    return (WFP_JSON_BOOL == json->type);
 }
 
 bool
 wfp_impl_json_is_int(
     struct wfp_json const * json)
 {
-    return ((NULL != json) && (WFP_JSON_INT == json->type));
+    return (WFP_JSON_INT == json->type);
 }
 
 bool
 wfp_impl_json_is_string(
     struct wfp_json const * json)
 {
-    return ((NULL != json) && (WFP_JSON_STRING == json->type));
+    return (WFP_JSON_STRING == json->type);
 }
 
 bool
 wfp_impl_json_is_array(
     struct wfp_json const * json)
 {
-    return ((NULL != json) && (WFP_JSON_ARRAY == json->type));
+    return (WFP_JSON_ARRAY == json->type);
 }
 
 bool
 wfp_impl_json_is_object(
     struct wfp_json const * json)
 {
-    return ((NULL != json) && (WFP_JSON_OBJECT == json->type));
+    return (WFP_JSON_OBJECT == json->type);
 }
 
 bool
@@ -102,7 +115,7 @@ wfp_impl_json_object_get(
         }
     }
 
-    return NULL;
+    return &wfp_json_null;
 }
 
 char const *
@@ -130,7 +143,7 @@ wfp_impl_json_object_value(
         return &(json->value.o.items[pos].json);
     }
 
-    return NULL;
+    return &wfp_json_null;
 }
 
 void
diff --git a/lib/webfuse_provider/impl/json/node.h b/lib/webfuse_provider/impl/json/node.h
index dc40888..6c12410 100644
--- a/lib/webfuse_provider/impl/json/node.h
+++ b/lib/webfuse_provider/impl/json/node.h
@@ -15,6 +15,10 @@ extern "C"
 
 struct wfp_json;
 
+extern bool
+wfp_impl_json_is_null(
+    struct wfp_json const * json);
+
 extern bool
 wfp_impl_json_is_bool(
     struct wfp_json const * json);
diff --git a/lib/webfuse_provider/impl/json/node_intern.h b/lib/webfuse_provider/impl/json/node_intern.h
index e043a88..b30556e 100644
--- a/lib/webfuse_provider/impl/json/node_intern.h
+++ b/lib/webfuse_provider/impl/json/node_intern.h
@@ -20,6 +20,7 @@ extern "C"
 
 enum wfp_json_type
 {
+    WFP_JSON_NULL,
     WFP_JSON_BOOL,
     WFP_JSON_INT,
     WFP_JSON_STRING,
diff --git a/lib/webfuse_provider/impl/jsonrpc/response.c b/lib/webfuse_provider/impl/jsonrpc/response.c
index c17900f..bc14c86 100644
--- a/lib/webfuse_provider/impl/jsonrpc/response.c
+++ b/lib/webfuse_provider/impl/jsonrpc/response.c
@@ -36,23 +36,24 @@ wfp_jsonrpc_response_init(
 	
 	result->id = wfp_impl_json_int_get(id_holder);
 	result->result = wfp_impl_json_object_get(response, "result");
-	if (NULL == result->result)
+	if (wfp_impl_json_is_null(result->result))
 	{
+		result->result = NULL;
+		int code = WFP_BAD_FORMAT;
+		char const * message = "invalid format: invalid error object";
+
 		struct wfp_json const * error = wfp_impl_json_object_get(response, "error");
 		if ((wfp_impl_json_is_object(error)) && (wfp_impl_json_is_int(wfp_impl_json_object_get(error, "code"))))
 		{
-			int code = wfp_impl_json_int_get(wfp_impl_json_object_get(error, "code"));
-			char const * message = "";
+			code = wfp_impl_json_int_get(wfp_impl_json_object_get(error, "code"));
+			message = "";
 			if (wfp_impl_json_is_string(wfp_impl_json_object_get(error, "message")))
 			{
 				message = wfp_impl_json_string_get(wfp_impl_json_object_get(error, "message"));
 			}
-			result->error = wfp_jsonrpc_error_create(code, message);
-		}
-		else
-		{
-			result->error = wfp_jsonrpc_error_create(WFP_BAD_FORMAT, "invalid format: invalid error object");
 		}
+
+		result->error = wfp_jsonrpc_error_create(code, message);
 	}
 }
 
diff --git a/test/webfuse_provider/mocks/mock_request.cc b/test/webfuse_provider/mocks/mock_request.cc
index 0202589..1337148 100644
--- a/test/webfuse_provider/mocks/mock_request.cc
+++ b/test/webfuse_provider/mocks/mock_request.cc
@@ -27,7 +27,7 @@ static void webfuse_test_MockRequest_respond(
             id = wfp_impl_json_int_get(id_holder);
         }
 
-        if (nullptr != result)
+        if (!wfp_impl_json_is_null(result))
         {
             error_code = WFP_GOOD;
             request->respond(result, id);