diff --git a/usr.bin/primes/primes.c b/usr.bin/primes/primes.c
index 76d166e9bda..1ce96d91201 100644
--- a/usr.bin/primes/primes.c
+++ b/usr.bin/primes/primes.c
@@ -241,6 +241,10 @@ primes(ubig start, ubig stop)
 		if (p <= pr_limit) {
 			return;
 		}
+		/*
+		 * the next odd number after the largest prime in the
+		 * precomputed list
+		 */
 		start = *pr_limit+2;
 	}