diff --git a/src/exactly_one_err.rs b/src/exactly_one_err.rs
index 51cfbc347..6b7bad56d 100644
--- a/src/exactly_one_err.rs
+++ b/src/exactly_one_err.rs
@@ -24,7 +24,7 @@ where
     I: Iterator,
 {
     /// Creates a new `ExactlyOneErr` iterator.
-    pub fn new(first_two: (Option<I::Item>, Option<I::Item>), inner: I) -> Self {
+    pub(crate) fn new(first_two: (Option<I::Item>, Option<I::Item>), inner: I) -> Self {
         Self { first_two, inner }
     }
 }
diff --git a/src/lib.rs b/src/lib.rs
index 59625a4c1..fa09d1028 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2056,7 +2056,7 @@ pub trait Itertools : Iterator {
     /// assert_eq!((0..10).filter(|&x| x == 2).exactly_one().unwrap(), 2);
     /// assert!((0..10).filter(|&x| x > 1 && x < 4).exactly_one().unwrap_err().eq(2..4));
     /// assert!((0..10).filter(|&x| x > 1 && x < 5).exactly_one().unwrap_err().eq(2..5));
-    /// assert!((0..10).filter(|&x| false).exactly_one().unwrap_err().eq(0..0));
+    /// assert!((0..10).filter(|&_| false).exactly_one().unwrap_err().eq(0..0));
     /// ```
     fn exactly_one(mut self) -> Result<Self::Item, ExactlyOneError<Self>>
     where
diff --git a/tests/quick.rs b/tests/quick.rs
index e0c61b47d..886c40533 100644
--- a/tests/quick.rs
+++ b/tests/quick.rs
@@ -1015,3 +1015,13 @@ quickcheck! {
         TestResult::from_bool(actual == expected)
     }
 }
+
+quickcheck! {
+    fn exactly_one_i32(a: Vec<i32>) -> TestResult {
+        let ret = a.iter().cloned().exactly_one();
+        match a.len() {
+            1 => TestResult::from_bool(ret.unwrap() == a[0]),
+            _ => TestResult::from_bool(ret.unwrap_err().eq(a.iter().cloned())),
+        }
+    }
+}
diff --git a/tests/test_core.rs b/tests/test_core.rs
index cf97abd36..7007217da 100644
--- a/tests/test_core.rs
+++ b/tests/test_core.rs
@@ -244,3 +244,11 @@ fn tree_fold1() {
         assert_eq!((0..i).tree_fold1(|x, y| x + y), (0..i).fold1(|x, y| x + y));
     }
 }
+
+#[test]
+fn exactly_one() {
+    assert_eq!((0..10).filter(|&x| x == 2).exactly_one().unwrap(), 2);
+    assert!((0..10).filter(|&x| x > 1 && x < 4).exactly_one().unwrap_err().eq(2..4));
+    assert!((0..10).filter(|&x| x > 1 && x < 5).exactly_one().unwrap_err().eq(2..5));
+    assert!((0..10).filter(|&_| false).exactly_one().unwrap_err().eq(0..0));
+}