diff --git a/crates/oxide_vm/src/vm_dispatch_misc.rs b/crates/oxide_vm/src/vm_dispatch_misc.rs
index b0310d25..abccbe82 100644
--- a/crates/oxide_vm/src/vm_dispatch_misc.rs
+++ b/crates/oxide_vm/src/vm_dispatch_misc.rs
@@ -1,4 +1,4 @@
-use std::sync::Arc;
+use std::sync::{Arc, OnceLock};
 
 use crate::native::NativeFn;
 use crate::vm::{native_fn_ptr_to_fn, CallFrame, ForInIter, FrameContinuation, Vm, MAX_PROTO_CHAIN_DEPTH};
@@ -153,6 +153,16 @@ impl Vm {
                 }
             }
 
+            let callee_subs = &subs[sub_idx].sub_modules;
+            if callee_subs.is_empty() {
+                self.sub_module_stack.push((Arc::clone(&self.sub_modules), None));
+            } else {
+                self.sub_module_stack
+                    .push((Arc::clone(&self.sub_modules), Some(std::mem::take(&mut self.immutables_cache))));
+                self.sub_modules = Arc::new(callee_subs.clone());
+                self.immutables_cache = (0..=callee_subs.len()).map(|_| OnceLock::new()).collect();
+            }
+
             self.active_reg_limit = sub_n_registers.max(1);
             self.pc = 0;
             Ok(true)