diff --git a/rust-toolchain b/rust-toolchain
index 65ee095..5422724 100644
--- a/rust-toolchain
+++ b/rust-toolchain
@@ -1 +1 @@
-1.67.0
+1.78.0
diff --git a/src/v4/relay.rs b/src/v4/relay.rs
index c2caea8..1412489 100644
--- a/src/v4/relay.rs
+++ b/src/v4/relay.rs
@@ -1,4 +1,4 @@
-//!
+//! # relay
 use std::{collections::HashMap, fmt, net::Ipv4Addr};
 
 use crate::{Decodable, Encodable};
diff --git a/src/v6/options.rs b/src/v6/options.rs
index 9857ef9..8ac4add 100644
--- a/src/v6/options.rs
+++ b/src/v6/options.rs
@@ -940,7 +940,7 @@ where
         let mid = (l + r) >> 1;
         // SAFETY: we know it is within the length
         let mid_cmp = f(unsafe { arr.get_unchecked(mid) });
-        let nxt_cmp = if mid < n {
+        let nxt_cmp = if mid < n && mid != n - 1 {
             f(unsafe { arr.get_unchecked(mid + 1) }) == Ordering::Greater
         } else {
             false
@@ -991,6 +991,12 @@ mod tests {
         let arr = vec![1, 2, 2, 2, 2, 3, 4, 7, 8, 8];
         assert_eq!(Some(7..=7), range_binsearch(&arr, |x| x.cmp(&7)));
 
+        let arr = vec![1, 2, 2, 2, 2, 3, 4, 7, 8, 9];
+        assert_eq!(Some(9..=9), range_binsearch(&arr, |x| x.cmp(&9)));
+
+        let arr = vec![1, 2, 2, 2, 2, 3, 4, 7, 9, 8];
+        assert_eq!(Some(0..=0), range_binsearch(&arr, |x| x.cmp(&1)));
+
         let arr: Vec<i32> = vec![];
         assert_eq!(None, range_binsearch(&arr, |x| x.cmp(&1)));