diff --git a/src/hashtable.h b/src/hashtable.h
index c112834..00d44a9 100644
--- a/src/hashtable.h
+++ b/src/hashtable.h
@@ -55,7 +55,7 @@ typedef struct hashtable {
  *
  * Returns 0 on success, -1 on error (out of memory).
  */
-int hashtable_init(hashtable_t *hashtable) JANSSON_ATTRS(warn_unused_result);
+int hashtable_init(hashtable_t *hashtable) JANSSON_ATTRS((warn_unused_result));
 
 /**
  * hashtable_close - Release all resources used by a hashtable object
diff --git a/src/jansson.h b/src/jansson.h
index b2b980b..54bf61b 100644
--- a/src/jansson.h
+++ b/src/jansson.h
@@ -40,9 +40,9 @@ extern "C" {
 #endif
 
 #if defined(__GNUC__) || defined(__clang__)
-#define JANSSON_ATTRS(...) __attribute__((__VA_ARGS__))
+#define JANSSON_ATTRS(x) __attribute__(x)
 #else
-#define JANSSON_ATTRS(...)
+#define JANSSON_ATTRS(x)
 #endif
 
 /* types */
@@ -191,7 +191,7 @@ static JSON_INLINE enum json_error_code json_error_code(const json_error_t *e) {
 
 void json_object_seed(size_t seed);
 size_t json_object_size(const json_t *object);
-json_t *json_object_get(const json_t *object, const char *key) JANSSON_ATTRS(warn_unused_result);
+json_t *json_object_get(const json_t *object, const char *key) JANSSON_ATTRS((warn_unused_result));
 int json_object_set_new(json_t *object, const char *key, json_t *value);
 int json_object_set_new_nocheck(json_t *object, const char *key, json_t *value);
 int json_object_del(json_t *object, const char *key);
@@ -243,7 +243,7 @@ int json_object_iter_set(json_t *object, void *iter, json_t *value)
 }
 
 size_t json_array_size(const json_t *array);
-json_t *json_array_get(const json_t *array, size_t index) JANSSON_ATTRS(warn_unused_result);
+json_t *json_array_get(const json_t *array, size_t index) JANSSON_ATTRS((warn_unused_result));
 int json_array_set_new(json_t *array, size_t index, json_t *value);
 int json_array_append_new(json_t *array, json_t *value);
 int json_array_insert_new(json_t *array, size_t index, json_t *value);
@@ -284,9 +284,9 @@ int json_real_set(json_t *real, double value);
 
 /* pack, unpack */
 
-json_t *json_pack(const char *fmt, ...) JANSSON_ATTRS(warn_unused_result);
-json_t *json_pack_ex(json_error_t *error, size_t flags, const char *fmt, ...) JANSSON_ATTRS(warn_unused_result);
-json_t *json_vpack_ex(json_error_t *error, size_t flags, const char *fmt, va_list ap) JANSSON_ATTRS(warn_unused_result);
+json_t *json_pack(const char *fmt, ...) JANSSON_ATTRS((warn_unused_result));
+json_t *json_pack_ex(json_error_t *error, size_t flags, const char *fmt, ...) JANSSON_ATTRS((warn_unused_result));
+json_t *json_vpack_ex(json_error_t *error, size_t flags, const char *fmt, va_list ap) JANSSON_ATTRS((warn_unused_result));
 
 #define JSON_VALIDATE_ONLY  0x1
 #define JSON_STRICT         0x2
@@ -297,8 +297,8 @@ int json_vunpack_ex(json_t *root, json_error_t *error, size_t flags, const char
 
 /* sprintf */
 
-json_t *json_sprintf(const char *fmt, ...) JANSSON_ATTRS(warn_unused_result, format(printf, 1, 2));
-json_t *json_vsprintf(const char *fmt, va_list ap) JANSSON_ATTRS(warn_unused_result, format(printf, 1, 0));
+json_t *json_sprintf(const char *fmt, ...) JANSSON_ATTRS((warn_unused_result, format(printf, 1, 2)));
+json_t *json_vsprintf(const char *fmt, va_list ap) JANSSON_ATTRS((warn_unused_result, format(printf, 1, 0)));
 
 
 /* equality */
@@ -308,8 +308,8 @@ int json_equal(const json_t *value1, const json_t *value2);
 
 /* copying */
 
-json_t *json_copy(json_t *value) JANSSON_ATTRS(warn_unused_result);
-json_t *json_deep_copy(const json_t *value) JANSSON_ATTRS(warn_unused_result);
+json_t *json_copy(json_t *value) JANSSON_ATTRS((warn_unused_result));
+json_t *json_deep_copy(const json_t *value) JANSSON_ATTRS((warn_unused_result));
 
 
 /* decoding */
@@ -322,12 +322,12 @@ json_t *json_deep_copy(const json_t *value) JANSSON_ATTRS(warn_unused_result);
 
 typedef size_t (*json_load_callback_t)(void *buffer, size_t buflen, void *data);
 
-json_t *json_loads(const char *input, size_t flags, json_error_t *error) JANSSON_ATTRS(warn_unused_result);
-json_t *json_loadb(const char *buffer, size_t buflen, size_t flags, json_error_t *error) JANSSON_ATTRS(warn_unused_result);
-json_t *json_loadf(FILE *input, size_t flags, json_error_t *error) JANSSON_ATTRS(warn_unused_result);
-json_t *json_loadfd(int input, size_t flags, json_error_t *error) JANSSON_ATTRS(warn_unused_result);
-json_t *json_load_file(const char *path, size_t flags, json_error_t *error) JANSSON_ATTRS(warn_unused_result);
-json_t *json_load_callback(json_load_callback_t callback, void *data, size_t flags, json_error_t *error) JANSSON_ATTRS(warn_unused_result);
+json_t *json_loads(const char *input, size_t flags, json_error_t *error) JANSSON_ATTRS((warn_unused_result));
+json_t *json_loadb(const char *buffer, size_t buflen, size_t flags, json_error_t *error) JANSSON_ATTRS((warn_unused_result));
+json_t *json_loadf(FILE *input, size_t flags, json_error_t *error) JANSSON_ATTRS((warn_unused_result));
+json_t *json_loadfd(int input, size_t flags, json_error_t *error) JANSSON_ATTRS((warn_unused_result));
+json_t *json_load_file(const char *path, size_t flags, json_error_t *error) JANSSON_ATTRS((warn_unused_result));
+json_t *json_load_callback(json_load_callback_t callback, void *data, size_t flags, json_error_t *error) JANSSON_ATTRS((warn_unused_result));
 
 
 /* encoding */
@@ -345,7 +345,7 @@ json_t *json_load_callback(json_load_callback_t callback, void *data, size_t fla
 
 typedef int (*json_dump_callback_t)(const char *buffer, size_t size, void *data);
 
-char *json_dumps(const json_t *json, size_t flags) JANSSON_ATTRS(warn_unused_result);
+char *json_dumps(const json_t *json, size_t flags) JANSSON_ATTRS((warn_unused_result));
 size_t json_dumpb(const json_t *json, char *buffer, size_t size, size_t flags);
 int json_dumpf(const json_t *json, FILE *output, size_t flags);
 int json_dumpfd(const json_t *json, int output, size_t flags);
diff --git a/src/jansson_private.h b/src/jansson_private.h
index c7ce11a..42882a8 100644
--- a/src/jansson_private.h
+++ b/src/jansson_private.h
@@ -84,11 +84,11 @@ int jsonp_strtod(strbuffer_t *strbuffer, double *out);
 int jsonp_dtostr(char *buffer, size_t size, double value, int prec);
 
 /* Wrappers for custom memory functions */
-void* jsonp_malloc(size_t size) JANSSON_ATTRS(warn_unused_result);
+void* jsonp_malloc(size_t size) JANSSON_ATTRS((warn_unused_result));
 void jsonp_free(void *ptr);
-char *jsonp_strndup(const char *str, size_t length) JANSSON_ATTRS(warn_unused_result);
-char *jsonp_strdup(const char *str) JANSSON_ATTRS(warn_unused_result);
-char *jsonp_strndup(const char *str, size_t len) JANSSON_ATTRS(warn_unused_result);
+char *jsonp_strndup(const char *str, size_t length) JANSSON_ATTRS((warn_unused_result));
+char *jsonp_strdup(const char *str) JANSSON_ATTRS((warn_unused_result));
+char *jsonp_strndup(const char *str, size_t len) JANSSON_ATTRS((warn_unused_result));
 
 /* Circular reference check*/
 /* Space for "0x", double the sizeof a pointer for the hex and a terminator. */
diff --git a/src/strbuffer.h b/src/strbuffer.h
index a0276d4..75c02a2 100644
--- a/src/strbuffer.h
+++ b/src/strbuffer.h
@@ -16,7 +16,7 @@ typedef struct {
     size_t size;     /* bytes allocated */
 } strbuffer_t;
 
-int strbuffer_init(strbuffer_t *strbuff) JANSSON_ATTRS(warn_unused_result);
+int strbuffer_init(strbuffer_t *strbuff) JANSSON_ATTRS((warn_unused_result));
 void strbuffer_close(strbuffer_t *strbuff);
 
 void strbuffer_clear(strbuffer_t *strbuff);