diff --git a/man2/getgroups.2 b/man2/getgroups.2
index a58a04a59..f880e3081 100644
--- a/man2/getgroups.2
+++ b/man2/getgroups.2
@@ -143,6 +143,10 @@ A process can have up to
 .B NGROUPS_MAX
 supplementary group IDs
 in addition to the effective group ID.
+The constant
+.B NGROUPS_MAX
+is defined in
+.IR <limits.h> .
 The set of supplementary group IDs
 is inherited from the parent process, and preserved across an
 .BR execve (2).