diff --git a/src/template/solaris b/src/template/solaris
index 07c79e9067..6114c3c1c8 100644
--- a/src/template/solaris
+++ b/src/template/solaris
@@ -10,6 +10,7 @@ case $host in
 esac
 
 # tools/thread/thread_test must be run
+# -D_POSIX_PTHREAD_SEMANTICS enables 5-arg getpwuid_r, among other things
 if test "$GCC" = yes 
 then	THREAD_CPPFLAGS="-D_POSIX_PTHREAD_SEMANTICS"
 	THREAD_LIBS="-pthread"