diff --git a/sys/include/string_utils.h b/sys/include/string_utils.h
index 69c530fbff..c8a399ae55 100644
--- a/sys/include/string_utils.h
+++ b/sys/include/string_utils.h
@@ -87,6 +87,7 @@ static inline const char *string_writer_str(const string_writer_t *sw)
     return sw->start;
 }
 
+#ifndef DOXYGEN
 /**
  * @brief   internal helper macro
  */
@@ -96,6 +97,8 @@ static inline const char *string_writer_str(const string_writer_t *sw)
 #define __swprintf swprintf
 __attribute__ ((format (printf, 2, 3)))
 #endif
+int __swprintf(string_writer_t *sw, FLASH_ATTR const char *restrict format, ...);
+#else
 /**
  * @brief   Write a formatted string to a buffer
  *          The string will be truncated if there is not enough space left in
@@ -106,9 +109,10 @@ __attribute__ ((format (printf, 2, 3)))
  * @param[in]   format  format string to write
  *
  * @return      number of bytes written on success
- *              -E2BIG if the string was truncated
+ * @retval      -E2BIG if the string was truncated
  */
-int __swprintf(string_writer_t *sw, FLASH_ATTR const char *restrict format, ...);
+int swprintf(string_writer_t *sw, FLASH_ATTR const char *restrict format, ...);
+#endif /* DOXYGEN */
 
 #if IS_ACTIVE(HAS_FLASH_UTILS_ARCH)
 #define swprintf(sw, fmt, ...) flash_swprintf(sw, TO_FLASH(fmt), ## __VA_ARGS__)