diff --git a/src/api/compile.rs b/src/api/compile.rs
index 4a3c0490..53402446 100644
--- a/src/api/compile.rs
+++ b/src/api/compile.rs
@@ -201,7 +201,11 @@ impl Engine {
         scope: &Scope,
         scripts: impl AsRef<[S]>,
     ) -> ParseResult<AST> {
-        self.compile_with_scope_and_optimization_level(scope, scripts, self.optimization_level)
+        self.compile_with_scope_and_optimization_level(
+            scope,
+            scripts,
+            self.options.optimization_level,
+        )
     }
     /// Join a list of strings and compile into an [`AST`] using own scope at a specific optimization level.
     ///
@@ -297,7 +301,12 @@ impl Engine {
 
         let mut peekable = stream.peekable();
         let mut state = ParseState::new(self, tokenizer_control);
-        self.parse_global_expr(&mut peekable, &mut state, scope, self.optimization_level)
+        self.parse_global_expr(
+            &mut peekable,
+            &mut state,
+            scope,
+            self.options.optimization_level,
+        )
     }
     /// Parse a JSON string into an [object map][crate::Map].
     /// This is a light-weight alternative to using, say,
diff --git a/src/api/eval.rs b/src/api/eval.rs
index 20d4655b..f83da77f 100644
--- a/src/api/eval.rs
+++ b/src/api/eval.rs
@@ -67,7 +67,7 @@ impl Engine {
         let ast = self.compile_with_scope_and_optimization_level(
             scope,
             &[script],
-            self.optimization_level,
+            self.options.optimization_level,
         )?;
         self.eval_ast_with_scope(scope, &ast)
     }
diff --git a/src/api/optimize.rs b/src/api/optimize.rs
index 7589c2fd..dd0ca118 100644
--- a/src/api/optimize.rs
+++ b/src/api/optimize.rs
@@ -9,7 +9,7 @@ impl Engine {
     /// Not available under `no_optimize`.
     #[inline(always)]
     pub fn set_optimization_level(&mut self, optimization_level: OptimizationLevel) -> &mut Self {
-        self.optimization_level = optimization_level;
+        self.options.optimization_level = optimization_level;
         self
     }
 
@@ -20,7 +20,7 @@ impl Engine {
     #[inline(always)]
     #[must_use]
     pub const fn optimization_level(&self) -> OptimizationLevel {
-        self.optimization_level
+        self.options.optimization_level
     }
 
     /// Optimize the [`AST`] with constants defined in an external Scope.
diff --git a/src/api/options.rs b/src/api/options.rs
index 619be34c..dba11f4b 100644
--- a/src/api/options.rs
+++ b/src/api/options.rs
@@ -1,12 +1,14 @@
 //! Settings for [`Engine`]'s language options.
 
-use crate::Engine;
+use crate::{Engine, OptimizationLevel};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
 
 /// A type containing all language options for the [`Engine`].
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
 pub struct LanguageOptions {
+    /// Script optimization level.
+    pub optimization_level: OptimizationLevel,
     /// Is `if`-expression allowed?
     pub allow_if_expr: bool,
     /// Is `switch` expression allowed?
@@ -33,6 +35,11 @@ impl LanguageOptions {
     #[inline(always)]
     pub const fn new() -> Self {
         Self {
+            #[cfg(not(feature = "no_optimize"))]
+            optimization_level: OptimizationLevel::Simple,
+            #[cfg(feature = "no_optimize")]
+            optimization_level: (),
+
             allow_if_expr: true,
             allow_switch_expr: true,
             allow_stmt_expr: true,
diff --git a/src/api/run.rs b/src/api/run.rs
index bad510a7..25fd69c7 100644
--- a/src/api/run.rs
+++ b/src/api/run.rs
@@ -30,7 +30,7 @@ impl Engine {
             &mut stream.peekable(),
             &mut state,
             scope,
-            self.optimization_level,
+            self.options.optimization_level,
         )?;
 
         self.run_ast_with_scope(scope, &ast)
diff --git a/src/engine.rs b/src/engine.rs
index 6b7614af..192416d0 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -9,8 +9,7 @@ use crate::packages::{Package, StandardPackage};
 use crate::tokenizer::Token;
 use crate::types::dynamic::Union;
 use crate::{
-    Dynamic, Identifier, ImmutableString, Module, OptimizationLevel, Position, RhaiResult, Shared,
-    StaticVec,
+    Dynamic, Identifier, ImmutableString, Module, Position, RhaiResult, Shared, StaticVec,
 };
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
@@ -129,9 +128,6 @@ pub struct Engine {
     #[cfg(not(feature = "unchecked"))]
     pub(crate) progress: Option<Box<crate::func::native::OnProgressCallback>>,
 
-    /// Optimize the [`AST`][crate::AST] after compilation.
-    pub(crate) optimization_level: OptimizationLevel,
-
     /// Language options.
     pub(crate) options: LanguageOptions,
 
@@ -167,9 +163,6 @@ impl fmt::Debug for Engine {
         #[cfg(not(feature = "unchecked"))]
         f.field("progress", &self.progress.is_some());
 
-        #[cfg(not(feature = "no_optimize"))]
-        f.field("optimization_level", &self.optimization_level);
-
         f.field("options", &self.options);
 
         #[cfg(not(feature = "unchecked"))]
@@ -274,8 +267,6 @@ impl Engine {
             #[cfg(not(feature = "unchecked"))]
             progress: None,
 
-            optimization_level: OptimizationLevel::default(),
-
             options: LanguageOptions::new(),
 
             #[cfg(not(feature = "unchecked"))]