diff --git a/man3/CPU_SET.3 b/man3/CPU_SET.3
index 285c40f4d..8558e92ea 100644
--- a/man3/CPU_SET.3
+++ b/man3/CPU_SET.3
@@ -284,6 +284,12 @@ while the
 argument of the
 .BR CPU_*_S ()
 macros is a size in bytes.
+
+The data types for arguments and return values shown
+in the SYNOPSIS are hints what about is expected in each case.
+However, since these these interfaces are implemented as macros,
+the compiler won't necessarily catch all type errors
+if you violate the suggestions.
 .SH EXAMPLE
 The following program demonstrates the use of some of the macros
 used for dynamically allocated CPU sets.