diff --git a/src/eval/expr.rs b/src/eval/expr.rs
index 60f81bf3..c3f1a5f4 100644
--- a/src/eval/expr.rs
+++ b/src/eval/expr.rs
@@ -92,13 +92,13 @@ impl Engine {
                     // global::VARIABLE
                     #[cfg(not(feature = "no_function"))]
                     if namespace.len() == 1 && namespace[0].name == crate::engine::KEYWORD_GLOBAL {
-                        let mut guard = crate::func::native::locked_write(&global.constants);
-
-                        if let Some(value) = guard.get_mut(var_name) {
-                            let mut target: Target = value.clone().into();
-                            // Module variables are constant
-                            target.set_access_mode(AccessMode::ReadOnly);
-                            return Ok((target.into(), *_var_pos));
+                        if let Some(ref constants) = global.constants {
+                            if let Some(value) = crate::func::locked_write(constants).get_mut(var_name) {
+                                let mut target: Target = value.clone().into();
+                                // Module variables are constant
+                                target.set_access_mode(AccessMode::ReadOnly);
+                                return Ok((target.into(), *_var_pos));
+                            }
                         }
 
                         return Err(ERR::ErrorVariableNotFound(
diff --git a/src/eval/global_state.rs b/src/eval/global_state.rs
index 4e7e33d4..ab32def5 100644
--- a/src/eval/global_state.rs
+++ b/src/eval/global_state.rs
@@ -42,9 +42,13 @@ pub struct GlobalRuntimeState<'a> {
     #[cfg(not(feature = "no_module"))]
     pub embedded_module_resolver: Option<Shared<crate::module::resolvers::StaticModuleResolver>>,
     /// Cache of globally-defined constants.
+    ///
+    /// Interior mutability is needed because it is shared in order to aid in cloning.
     #[cfg(not(feature = "no_module"))]
     #[cfg(not(feature = "no_function"))]
-    pub(crate) constants: crate::Locked<std::collections::BTreeMap<Identifier, crate::Dynamic>>,
+    pub(crate) constants: Option<
+        crate::Shared<crate::Locked<std::collections::BTreeMap<Identifier, crate::Dynamic>>>,
+    >,
     /// Debugging interface.
     #[cfg(feature = "debugging")]
     pub debugger: super::Debugger,
@@ -71,7 +75,7 @@ impl GlobalRuntimeState<'_> {
             fn_hash_indexing: (0, 0),
             #[cfg(not(feature = "no_module"))]
             #[cfg(not(feature = "no_function"))]
-            constants: std::collections::BTreeMap::new().into(),
+            constants: None,
             #[cfg(feature = "debugging")]
             debugger: crate::eval::Debugger::new(_engine),
             dummy: PhantomData::default(),
diff --git a/src/eval/stmt.rs b/src/eval/stmt.rs
index badfa8cc..df8894b4 100644
--- a/src/eval/stmt.rs
+++ b/src/eval/stmt.rs
@@ -818,7 +818,12 @@ impl Engine {
                             && entry_type == AccessMode::ReadOnly
                             && lib.iter().any(|&m| !m.is_empty())
                         {
-                            crate::func::native::locked_write(&global.constants)
+                            if global.constants.is_none() {
+                                global.constants = Some(crate::Shared::new(crate::Locked::new(
+                                    std::collections::BTreeMap::new(),
+                                )));
+                            }
+                            crate::func::locked_write(global.constants.as_ref().unwrap())
                                 .insert(var_name.clone(), value.clone());
                         }
 
diff --git a/src/module/mod.rs b/src/module/mod.rs
index 0a613af4..26049a1f 100644
--- a/src/module/mod.rs
+++ b/src/module/mod.rs
@@ -1685,7 +1685,6 @@ impl Module {
         // Save global state
         let orig_imports_len = global.num_imports();
         let orig_source = global.source.clone();
-        #[cfg(not(feature = "no_module"))]
         #[cfg(not(feature = "no_function"))]
         let orig_constants = std::mem::take(&mut global.constants);
 
@@ -1719,7 +1718,6 @@ impl Module {
         }
 
         // Restore global state
-        #[cfg(not(feature = "no_module"))]
         #[cfg(not(feature = "no_function"))]
         {
             global.constants = orig_constants;