diff --git a/CHANGELOG.md b/CHANGELOG.md
index 97aea371..e594d41e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -34,6 +34,7 @@ Enhancements
 * `range` function now supports negative step and decreasing streams (i.e. to < from).
 * More information is provided to the error variable captured by the `catch` statement in an _object map_.
 * Previously, `private` functions in an `AST` cannot be called with `call_fn` etc. This is inconvenient when trying to call a function inside a script which also serves as a loadable module exporting part (but not all) of the functions. Now, all functions (`private` or not) can be called in an `AST`. The `private` keyword is relegated to preventing a function from being exported.
+* `Dynamic::as_unit` just for completeness sake.
 
 
 Version 0.19.13
diff --git a/src/dynamic.rs b/src/dynamic.rs
index b0168ccb..47fe3e2d 100644
--- a/src/dynamic.rs
+++ b/src/dynamic.rs
@@ -134,17 +134,6 @@ pub enum AccessMode {
     ReadOnly,
 }
 
-impl AccessMode {
-    /// Is the access type `ReadOnly`?
-    #[inline(always)]
-    pub fn is_read_only(self) -> bool {
-        match self {
-            Self::ReadWrite => false,
-            Self::ReadOnly => true,
-        }
-    }
-}
-
 /// Dynamic type containing any value.
 pub struct Dynamic(pub(crate) Union);
 
@@ -748,17 +737,25 @@ impl Dynamic {
     pub fn is_read_only(&self) -> bool {
         match self.0 {
             #[cfg(not(feature = "no_closure"))]
-            Union::Shared(_, access) if access.is_read_only() => true,
+            Union::Shared(_, AccessMode::ReadOnly) => true,
 
             #[cfg(not(feature = "no_closure"))]
-            #[cfg(not(feature = "sync"))]
-            Union::Shared(ref cell, _) => cell.borrow().access_mode().is_read_only(),
+            Union::Shared(ref cell, _) => {
+                #[cfg(not(feature = "sync"))]
+                let access = cell.borrow().access_mode();
+                #[cfg(feature = "sync")]
+                let access = cell.read().unwrap().access_mode();
 
-            #[cfg(not(feature = "no_closure"))]
-            #[cfg(feature = "sync")]
-            Union::Shared(ref cell, _) => cell.read().unwrap().access_mode().is_read_only(),
+                match access {
+                    AccessMode::ReadWrite => false,
+                    AccessMode::ReadOnly => true,
+                }
+            }
 
-            _ => self.access_mode().is_read_only(),
+            _ => match self.access_mode() {
+                AccessMode::ReadWrite => false,
+                AccessMode::ReadOnly => true,
+            },
         }
     }
     /// Can this [`Dynamic`] be hashed?
@@ -1439,6 +1436,17 @@ impl Dynamic {
             _ => None,
         }
     }
+    /// Cast the [`Dynamic`] as a unit `()` and return it.
+    /// Returns the name of the actual type if the cast fails.
+    #[inline(always)]
+    pub fn as_unit(&self) -> Result<(), &'static str> {
+        match self.0 {
+            Union::Unit(value, _) => Ok(value),
+            #[cfg(not(feature = "no_closure"))]
+            Union::Shared(_, _) => self.read_lock().map(|v| *v).ok_or_else(|| self.type_name()),
+            _ => Err(self.type_name()),
+        }
+    }
     /// Cast the [`Dynamic`] as the system integer type [`INT`] and return it.
     /// Returns the name of the actual type if the cast fails.
     #[inline(always)]
diff --git a/src/optimize.rs b/src/optimize.rs
index b484e643..cff6580b 100644
--- a/src/optimize.rs
+++ b/src/optimize.rs
@@ -113,17 +113,16 @@ impl<'a> State<'a> {
             return None;
         }
 
-        for (n, access, expr) in self.variables.iter().rev() {
+        self.variables.iter().rev().find_map(|(n, access, expr)| {
             if n == name {
-                return if access.is_read_only() {
-                    Some(expr)
-                } else {
-                    None
-                };
+                match access {
+                    AccessMode::ReadWrite => None,
+                    AccessMode::ReadOnly => Some(expr),
+                }
+            } else {
+                None
             }
-        }
-
-        None
+        })
     }
 }