diff --git a/src/kv/source.rs b/src/kv/source.rs
index 2a26c4a05..c8e7a05a3 100644
--- a/src/kv/source.rs
+++ b/src/kv/source.rs
@@ -30,14 +30,10 @@ pub trait Source {
     ///
     /// A source that can provide a more efficient implementation of this method
     /// should override it.
-    #[cfg(not(test))]
     fn get(&self, key: Key) -> Option<Value<'_>> {
         get_default(self, key)
     }
 
-    #[cfg(test)]
-    fn get(&self, key: Key) -> Option<Value<'_>>;
-
     /// Count the number of key-value pairs that can be visited.
     ///
     /// # Implementation notes
@@ -47,17 +43,13 @@ pub trait Source {
     ///
     /// A subsequent call to `visit` should yield the same number of key-value pairs
     /// to the visitor, unless that visitor fails part way through.
-    #[cfg(not(test))]
     fn count(&self) -> usize {
         count_default(self)
     }
-
-    #[cfg(test)]
-    fn count(&self) -> usize;
 }
 
 /// The default implementation of `Source::get`
-pub(crate) fn get_default<'v>(source: &'v (impl Source + ?Sized), key: Key) -> Option<Value<'v>> {
+fn get_default<'v>(source: &'v (impl Source + ?Sized), key: Key) -> Option<Value<'v>> {
     struct Get<'k, 'v> {
         key: Key<'k>,
         found: Option<Value<'v>>,
@@ -80,7 +72,7 @@ pub(crate) fn get_default<'v>(source: &'v (impl Source + ?Sized), key: Key) -> O
 }
 
 /// The default implementation of `Source::count`.
-pub(crate) fn count_default(source: impl Source) -> usize {
+fn count_default(source: impl Source) -> usize {
     struct Count(usize);
 
     impl<'kvs> Visitor<'kvs> for Count {
@@ -158,7 +150,7 @@ where
     }
 
     fn count(&self) -> usize {
-        self.len()
+        self.iter().map(Source::count).sum()
     }
 }
 
@@ -167,7 +159,7 @@ where
     S: Source,
 {
     fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
-        if let Some(ref source) = *self {
+        if let Some(source) = self {
             source.visit(visitor)?;
         }
 
@@ -233,6 +225,8 @@ mod std_support {
     use std::borrow::Borrow;
     use std::collections::{BTreeMap, HashMap};
     use std::hash::{BuildHasher, Hash};
+    use std::rc::Rc;
+    use std::sync::Arc;
 
     impl<S> Source for Box<S>
     where
@@ -251,6 +245,40 @@ mod std_support {
         }
     }
 
+    impl<S> Source for Arc<S>
+    where
+        S: Source + ?Sized,
+    {
+        fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+            Source::visit(&**self, visitor)
+        }
+
+        fn get(&self, key: Key) -> Option<Value<'_>> {
+            Source::get(&**self, key)
+        }
+
+        fn count(&self) -> usize {
+            Source::count(&**self)
+        }
+    }
+
+    impl<S> Source for Rc<S>
+    where
+        S: Source + ?Sized,
+    {
+        fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
+            Source::visit(&**self, visitor)
+        }
+
+        fn get(&self, key: Key) -> Option<Value<'_>> {
+            Source::get(&**self, key)
+        }
+
+        fn count(&self) -> usize {
+            Source::count(&**self)
+        }
+    }
+
     impl<S> Source for Vec<S>
     where
         S: Source,
@@ -714,14 +742,6 @@ mod tests {
             fn visit<'kvs>(&'kvs self, visitor: &mut dyn Visitor<'kvs>) -> Result<(), Error> {
                 visitor.visit_pair(self.key.to_key(), self.value.to_value())
             }
-
-            fn get(&self, key: Key) -> Option<Value<'_>> {
-                get_default(self, key)
-            }
-
-            fn count(&self) -> usize {
-                count_default(self)
-            }
         }
 
         assert_eq!(1, Source::count(&("a", 1)));
diff --git a/src/kv/value.rs b/src/kv/value.rs
index d4c45ea7f..352f965ea 100644
--- a/src/kv/value.rs
+++ b/src/kv/value.rs
@@ -470,14 +470,14 @@ impl<'v> From<&'v i128> for Value<'v> {
 impl<'v> From<&'v std::num::NonZeroU128> for Value<'v> {
     fn from(v: &'v std::num::NonZeroU128) -> Value<'v> {
         // SAFETY: `NonZeroU128` and `u128` have the same ABI
-        Value::from_value_bag(unsafe { std::mem::transmute::<&std::num::NonZeroU128, &u128>(v) })
+        Value::from_value_bag(unsafe { &*(v as *const std::num::NonZeroU128 as *const u128) })
     }
 }
 
 impl<'v> From<&'v std::num::NonZeroI128> for Value<'v> {
     fn from(v: &'v std::num::NonZeroI128) -> Value<'v> {
         // SAFETY: `NonZeroI128` and `i128` have the same ABI
-        Value::from_value_bag(unsafe { std::mem::transmute::<&std::num::NonZeroI128, &i128>(v) })
+        Value::from_value_bag(unsafe { &*(v as *const std::num::NonZeroI128 as *const i128) })
     }
 }
 
@@ -589,6 +589,8 @@ impl<'v> Value<'v> {
 #[cfg(feature = "kv_unstable_std")]
 mod std_support {
     use std::borrow::Cow;
+    use std::rc::Rc;
+    use std::sync::Arc;
 
     use super::*;
 
@@ -601,6 +603,24 @@ mod std_support {
         }
     }
 
+    impl<T> ToValue for Arc<T>
+    where
+        T: ToValue + ?Sized,
+    {
+        fn to_value(&self) -> Value {
+            (**self).to_value()
+        }
+    }
+
+    impl<T> ToValue for Rc<T>
+    where
+        T: ToValue + ?Sized,
+    {
+        fn to_value(&self) -> Value {
+            (**self).to_value()
+        }
+    }
+
     impl ToValue for String {
         fn to_value(&self) -> Value {
             Value::from(&**self)