diff --git a/src/urlencoded/de/val_or_vec.rs b/src/urlencoded/de/val_or_vec.rs
index 0e8409a0..ee2c4181 100644
--- a/src/urlencoded/de/val_or_vec.rs
+++ b/src/urlencoded/de/val_or_vec.rs
@@ -234,3 +234,31 @@ where
         deserialize_map,
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::borrow::Cow;
+
+    use matches::assert_matches;
+
+    use super::ValOrVec;
+
+    #[test]
+    fn cow_borrowed() {
+        let mut x = ValOrVec::Val(Cow::Borrowed("a"));
+        x.push(Cow::Borrowed("b"));
+        x.push(Cow::Borrowed("c"));
+        assert_matches!(x, ValOrVec::Vec(v) if v == vec!["a", "b", "c"]);
+    }
+
+    #[test]
+    fn cow_owned() {
+        let mut x = ValOrVec::Val(Cow::from("a".to_owned()));
+        x.push(Cow::from("b".to_owned()));
+        x.push(Cow::from("c".to_owned()));
+        assert_matches!(
+            x,
+            ValOrVec::Vec(v) if v == vec!["a".to_owned(), "b".to_owned(), "c".to_owned()]
+        );
+    }
+}