diff --git a/src/impls/columns.rs b/src/impls/columns.rs
index bf6d43d..32a8170 100644
--- a/src/impls/columns.rs
+++ b/src/impls/columns.rs
@@ -267,16 +267,18 @@ where
 {
     type Owned = Vec<R::Owned>;
 
-    fn into_owned(self) -> Self::Owned {
-        self.iter().map(IntoOwned::into_owned).collect()
+    fn into_owned(&self) -> Self::Owned {
+        self.iter()
+            .map(|item| IntoOwned::into_owned(&item))
+            .collect()
     }
 
-    fn clone_onto(self, other: &mut Self::Owned) {
+    fn clone_onto(&self, other: &mut Self::Owned) {
         let r = std::cmp::min(self.len(), other.len());
         for (item, target) in self.iter().zip(other.iter_mut()) {
             item.clone_onto(target);
         }
-        other.extend(self.iter().skip(r).map(IntoOwned::into_owned));
+        other.extend(self.iter().skip(r).map(|item| IntoOwned::into_owned(&item)));
         other.truncate(self.len());
     }
 
diff --git a/src/impls/mirror.rs b/src/impls/mirror.rs
index 8ea70f0..ace235d 100644
--- a/src/impls/mirror.rs
+++ b/src/impls/mirror.rs
@@ -151,12 +151,12 @@ macro_rules! implement_for {
         impl<'a> IntoOwned<'a> for $index_type {
             type Owned = $index_type;
 
-            fn into_owned(self) -> Self::Owned {
-                self
+            fn into_owned(&self) -> Self::Owned {
+                *self
             }
 
-            fn clone_onto(self, other: &mut Self::Owned) {
-                *other = self;
+            fn clone_onto(&self, other: &mut Self::Owned) {
+                *other = *self;
             }
 
             fn borrow_as(owned: &'a Self::Owned) -> Self {
diff --git a/src/impls/option.rs b/src/impls/option.rs
index 04599e3..c534305 100644
--- a/src/impls/option.rs
+++ b/src/impls/option.rs
@@ -82,11 +82,11 @@ where
 {
     type Owned = Option<T::Owned>;
 
-    fn into_owned(self) -> Self::Owned {
-        self.map(IntoOwned::into_owned)
+    fn into_owned(&self) -> Self::Owned {
+        self.as_ref().map(IntoOwned::into_owned)
     }
 
-    fn clone_onto(self, other: &mut Self::Owned) {
+    fn clone_onto(&self, other: &mut Self::Owned) {
         match (self, other) {
             (Some(item), Some(target)) => T::clone_onto(item, target),
             (Some(item), target) => *target = Some(T::into_owned(item)),
diff --git a/src/impls/result.rs b/src/impls/result.rs
index 755e147..975c6b3 100644
--- a/src/impls/result.rs
+++ b/src/impls/result.rs
@@ -95,11 +95,11 @@ where
 {
     type Owned = Result<T::Owned, E::Owned>;
 
-    fn into_owned(self) -> Self::Owned {
-        self.map(T::into_owned).map_err(E::into_owned)
+    fn into_owned(&self) -> Self::Owned {
+        self.as_ref().map(T::into_owned).map_err(E::into_owned)
     }
 
-    fn clone_onto(self, other: &mut Self::Owned) {
+    fn clone_onto(&self, other: &mut Self::Owned) {
         match (self, other) {
             (Ok(item), Ok(target)) => T::clone_onto(item, target),
             (Err(item), Err(target)) => E::clone_onto(item, target),
diff --git a/src/impls/slice.rs b/src/impls/slice.rs
index 4759da7..e009ebc 100644
--- a/src/impls/slice.rs
+++ b/src/impls/slice.rs
@@ -241,16 +241,18 @@ where
 {
     type Owned = Vec<C::Owned>;
 
-    fn into_owned(self) -> Self::Owned {
-        self.iter().map(IntoOwned::into_owned).collect()
+    fn into_owned(&self) -> Self::Owned {
+        self.iter()
+            .map(|item| IntoOwned::into_owned(&item))
+            .collect()
     }
 
-    fn clone_onto(self, other: &mut Self::Owned) {
+    fn clone_onto(&self, other: &mut Self::Owned) {
         let r = std::cmp::min(self.len(), other.len());
         for (item, target) in self.iter().zip(other.iter_mut()) {
             item.clone_onto(target);
         }
-        other.extend(self.iter().skip(r).map(IntoOwned::into_owned));
+        other.extend(self.iter().skip(r).map(|item| IntoOwned::into_owned(&item)));
         other.truncate(self.len());
     }
 
diff --git a/src/impls/tuple.rs b/src/impls/tuple.rs
index acbe4fb..16febfa 100644
--- a/src/impls/tuple.rs
+++ b/src/impls/tuple.rs
@@ -108,14 +108,14 @@ macro_rules! tuple_flatcontainer {
             {
                 type Owned = ($($name::Owned,)*);
 
-                fn into_owned(self) -> Self::Owned {
+                fn into_owned(&self) -> Self::Owned {
                     let ($($name,)*) = self;
                     (
                         $($name.into_owned(),)*
                     )
                 }
 
-                fn clone_onto(self, other: &mut Self::Owned) {
+                fn clone_onto(&self, other: &mut Self::Owned) {
                     let ($($name,)*) = self;
                     let ($([<$name _other>],)*) = other;
                     $($name.clone_onto([<$name _other>]);)*
diff --git a/src/lib.rs b/src/lib.rs
index 3c39097..e4f99de 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -113,19 +113,22 @@ pub trait IntoOwned<'a> {
     /// Owned type into which this type can be converted.
     type Owned;
     /// Conversion from an instance of this type to the owned type.
-    fn into_owned(self) -> Self::Owned;
+    fn into_owned(&self) -> Self::Owned;
     /// Clones `self` onto an existing instance of the owned type.
-    fn clone_onto(self, other: &mut Self::Owned);
+    fn clone_onto(&self, other: &mut Self::Owned);
     /// Borrows an owned instance as oneself.
     fn borrow_as(owned: &'a Self::Owned) -> Self;
 }
 
-impl<'a, T: ToOwned + ?Sized> IntoOwned<'a> for &'a T {
+impl<'a, T> IntoOwned<'a> for &'a T
+where
+    T: ToOwned + ?Sized,
+{
     type Owned = T::Owned;
-    fn into_owned(self) -> Self::Owned {
-        self.to_owned()
+    fn into_owned(&self) -> Self::Owned {
+        (*self).to_owned()
     }
-    fn clone_onto(self, other: &mut Self::Owned) {
+    fn clone_onto(&self, other: &mut Self::Owned) {
         <T as ToOwned>::clone_into(self, other)
     }
     fn borrow_as(owned: &'a Self::Owned) -> Self {
@@ -435,7 +438,7 @@ mod tests {
     impl<'a> IntoOwned<'a> for PersonRef<'a> {
         type Owned = Person;
 
-        fn into_owned(self) -> Self::Owned {
+        fn into_owned(&self) -> Self::Owned {
             Person {
                 name: self.name.into_owned(),
                 age: self.age,
@@ -443,7 +446,7 @@ mod tests {
             }
         }
 
-        fn clone_onto(self, other: &mut Self::Owned) {
+        fn clone_onto(&self, other: &mut Self::Owned) {
             self.name.clone_onto(&mut other.name);
             other.age = self.age;
             self.hobbies.clone_onto(&mut other.hobbies);
@@ -766,8 +769,7 @@ mod tests {
             for<'a> R: Region + Push<<<R as Region>::ReadItem<'a> as IntoOwned<'a>>::Owned>,
             for<'a> R::ReadItem<'a>: IntoOwned<'a, Owned = O> + Eq + Debug,
         {
-            let item = region.index(index);
-            let owned = item.into_owned();
+            let owned = region.index(index).into_owned();
             let index2 = region.push(owned);
             let item = region.index(index);
             assert_eq!(item, region.index(index2));