--- a/crates/jrsonnet-evaluator/src/ctx.rs
+++ b/crates/jrsonnet-evaluator/src/ctx.rs
@@ -75,36 +75,56 @@
 		ctx.unwrap()
 	}
 
-	pub fn with_var(&self, name: Rc<str>, value: Val) -> Result<Context> {
+	pub fn with_var(self, name: Rc<str>, value: Val) -> Context {
 		let mut new_bindings = HashMap::with_capacity(1);
 		new_bindings.insert(name, resolved_lazy_val!(value));
 		self.extend(new_bindings, None, None, None)
 	}
 
 	pub fn extend(
-		&self,
+		self,
 		new_bindings: HashMap<Rc<str>, LazyVal>,
 		new_dollar: Option<ObjValue>,
 		new_this: Option<ObjValue>,
 		new_super_obj: Option<ObjValue>,
-	) -> Result<Context> {
-		let dollar = new_dollar.or_else(|| self.0.dollar.clone());
-		let this = new_this.or_else(|| self.0.this.clone());
-		let super_obj = new_super_obj.or_else(|| self.0.super_obj.clone());
-		let bindings = if new_bindings.is_empty() {
-			self.0.bindings.clone()
-		} else {
-			self.0.bindings.extend(new_bindings)
-		};
-		Ok(Context(Rc::new(ContextInternals {
-			dollar,
-			this,
-			super_obj,
-			bindings,
-		})))
+	) -> Context {
+		match Rc::try_unwrap(self.0) {
+			Ok(mut ctx) => {
+				// Extended context aren't used by anything else, we can freely mutate it without cloning
+				if let Some(dollar) = new_dollar {
+					ctx.dollar = Some(dollar);
+				}
+				if let Some(this) = new_this {
+					ctx.this = Some(this);
+				}
+				if let Some(super_obj) = new_super_obj {
+					ctx.super_obj = Some(super_obj);
+				}
+				if !new_bindings.is_empty() {
+					ctx.bindings = ctx.bindings.extend(new_bindings);
+				}
+				Context(Rc::new(ctx))
+			}
+			Err(ctx) => {
+				let dollar = new_dollar.or_else(|| ctx.dollar.clone());
+				let this = new_this.or_else(|| ctx.this.clone());
+				let super_obj = new_super_obj.or_else(|| ctx.super_obj.clone());
+				let bindings = if new_bindings.is_empty() {
+					ctx.bindings.clone()
+				} else {
+					ctx.bindings.clone().extend(new_bindings)
+				};
+				Context(Rc::new(ContextInternals {
+					dollar,
+					this,
+					super_obj,
+					bindings,
+				}))
+			}
+		}
 	}
 	pub fn extend_unbound(
-		&self,
+		self,
 		new_bindings: HashMap<Rc<str>, LazyBinding>,
 		new_dollar: Option<ObjValue>,
 		new_this: Option<ObjValue>,
@@ -116,7 +136,7 @@
 		for (k, v) in new_bindings.into_iter() {
 			new.insert(k, v.evaluate(this.clone(), super_obj.clone())?);
 		}
-		self.extend(new, new_dollar, this, super_obj)
+		Ok(self.extend(new, new_dollar, this, super_obj))
 	}
 	pub fn into_weak(self) -> WeakContext {
 		WeakContext(Rc::downgrade(&self.0))
--- a/crates/jrsonnet-evaluator/src/evaluate.rs
+++ b/crates/jrsonnet-evaluator/src/evaluate.rs
@@ -209,7 +209,7 @@
 					for item in list.iter() {
 						let item = item.unwrap_if_lazy()?;
 						out.push(evaluate_comp(
-							context.with_var(var.clone(), item.clone())?,
+							context.clone().with_var(var.clone(), item.clone()),
 							value,
 							&specs[1..],
 						)?);
@@ -227,7 +227,7 @@
 	let future_this = FutureObjValue::new();
 	let context_creator = context_creator!(
 		closure!(clone context, clone new_bindings, |this: Option<ObjValue>, super_obj: Option<ObjValue>| {
-			Ok(context.extend_unbound(
+			Ok(context.clone().extend_unbound(
 				new_bindings.clone().unwrap(),
 				context.dollar().clone().or_else(||this.clone()),
 				Some(this.unwrap()),
@@ -332,7 +332,7 @@
 					let new_bindings = FutureNewBindings::new();
 					let context_creator = context_creator!(
 						closure!(clone context, clone new_bindings, |this: Option<ObjValue>, super_obj: Option<ObjValue>| {
-							Ok(context.extend_unbound(
+							Ok(context.clone().extend_unbound(
 								new_bindings.clone().unwrap(),
 								context.dollar().clone().or_else(||this.clone()),
 								None,
@@ -354,7 +354,7 @@
 					let key = evaluate(ctx.clone(), &obj.key)?;
 					let value = LazyBinding::Bindable(Rc::new(
 						closure!(clone ctx, clone obj.value, |this, _super_obj| {
-							Ok(LazyVal::new_resolved(evaluate(ctx.extend(HashMap::new(), None, this, None)?, &value)?))
+							Ok(LazyVal::new_resolved(evaluate(ctx.clone().extend(HashMap::new(), None, this, None), &value)?))
 						}),
 					));
 
--- a/crates/jrsonnet-evaluator/src/function.rs
+++ b/crates/jrsonnet-evaluator/src/function.rs
@@ -57,7 +57,7 @@
 		out.insert(p.0.clone(), val);
 	}
 
-	Ok(body_ctx.unwrap_or(ctx).extend(out, None, None, None)?)
+	Ok(body_ctx.unwrap_or(ctx).extend(out, None, None, None))
 }
 
 pub fn parse_function_call_map(
@@ -106,7 +106,7 @@
 		out.insert(p.0.clone(), val);
 	}
 
-	Ok(body_ctx.unwrap_or(ctx).extend(out, None, None, None)?)
+	Ok(body_ctx.unwrap_or(ctx).extend(out, None, None, None))
 }
 
 pub(crate) fn place_args(
@@ -135,7 +135,7 @@
 		out.insert(p.0.clone(), resolved_lazy_val!(val));
 	}
 
-	Ok(body_ctx.unwrap_or(ctx).extend(out, None, None, None)?)
+	Ok(body_ctx.unwrap_or(ctx).extend(out, None, None, None))
 }
 
 #[macro_export]
--- a/crates/jrsonnet-evaluator/src/map.rs
+++ b/crates/jrsonnet-evaluator/src/map.rs
@@ -10,12 +10,17 @@
 pub struct LayeredHashMap<K: Hash, V>(Rc<LayeredHashMapInternals<K, V>>);
 
 impl<K: Hash + Eq, V> LayeredHashMap<K, V> {
-	pub fn extend(&self, new_layer: HashMap<K, V>) -> Self {
-		let super_map = self.clone();
-		LayeredHashMap(Rc::new(LayeredHashMapInternals {
-			parent: Some(super_map),
-			current: new_layer,
-		}))
+	pub fn extend(self, new_layer: HashMap<K, V>) -> Self {
+		match Rc::try_unwrap(self.0) {
+			Ok(mut map) => {
+				map.current.extend(new_layer);
+				LayeredHashMap(Rc::new(map))
+			}
+			Err(this) => LayeredHashMap(Rc::new(LayeredHashMapInternals {
+				parent: Some(LayeredHashMap(this)),
+				current: new_layer,
+			})),
+		}
 	}
 
 	pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V>