diff --git a/os/rt/include/chthreads.h b/os/rt/include/chthreads.h
index 0fd206d19..6ac40d3b8 100644
--- a/os/rt/include/chthreads.h
+++ b/os/rt/include/chthreads.h
@@ -182,6 +182,9 @@ typedef struct {
  * @note    The specified time is rounded up to a value allowed by the real
  *          system tick clock.
  * @note    The maximum specifiable value is implementation dependent.
+ * @note    Use of this macro for large values is not secure because
+ *          integer overflows, make sure your value can be correctly
+ *          converted.
  *
  * @param[in] sec       time in seconds, must be different from zero
  *
@@ -195,6 +198,9 @@ typedef struct {
  * @note    The specified time is rounded up to a value allowed by the real
  *          system tick clock.
  * @note    The maximum specifiable value is implementation dependent.
+ * @note    Use of this macro for large values is not secure because
+ *          integer overflows, make sure your value can be correctly
+ *          converted.
  *
  * @param[in] msec      time in milliseconds, must be different from zero
  *
@@ -208,6 +214,9 @@ typedef struct {
  * @note    The specified time is rounded up to a value allowed by the real
  *          system tick clock.
  * @note    The maximum specifiable value is implementation dependent.
+ * @note    Use of this macro for large values is not secure because
+ *          integer overflows, make sure your value can be correctly
+ *          converted.
  *
  * @param[in] usec      time in microseconds, must be different from zero
  *