diff --git a/compiler/gen/src/llvm/build.rs b/compiler/gen/src/llvm/build.rs
index 8f7b9d8081..c407d60ec3 100644
--- a/compiler/gen/src/llvm/build.rs
+++ b/compiler/gen/src/llvm/build.rs
@@ -31,7 +31,7 @@ use inkwell::OptimizationLevel;
 use inkwell::{AddressSpace, IntPredicate};
 use roc_collections::all::{ImMap, MutSet};
 use roc_module::low_level::LowLevel;
-use roc_module::symbol::{Interns, Symbol};
+use roc_module::symbol::{Interns, ModuleId, Symbol};
 use roc_mono::ir::{JoinPointId, Wrapped};
 use roc_mono::layout::{Builtin, Layout, MemoryMode};
 use target_lexicon::CallingConvention;
@@ -53,6 +53,7 @@ pub enum OptLevel {
 #[derive(Default, Debug, Clone, PartialEq)]
 pub struct Scope<'a, 'ctx> {
     symbols: ImMap<Symbol, (Layout<'a>, PointerValue<'ctx>)>,
+    pub top_level_thunks: ImMap<Symbol, (Layout<'a>, FunctionValue<'ctx>)>,
     join_points: ImMap<JoinPointId, (BasicBlock<'ctx>, &'a [PointerValue<'ctx>])>,
 }
 
@@ -63,23 +64,23 @@ impl<'a, 'ctx> Scope<'a, 'ctx> {
     pub fn insert(&mut self, symbol: Symbol, value: (Layout<'a>, PointerValue<'ctx>)) {
         self.symbols.insert(symbol, value);
     }
+    pub fn insert_top_level_thunk(
+        &mut self,
+        symbol: Symbol,
+        layout: Layout<'a>,
+        function_value: FunctionValue<'ctx>,
+    ) {
+        self.top_level_thunks
+            .insert(symbol, (layout, function_value));
+    }
     fn remove(&mut self, symbol: &Symbol) {
         self.symbols.remove(symbol);
     }
-    /*
-    fn get_join_point(&self, symbol: &JoinPointId) -> Option<&PhiValue<'ctx>> {
-        self.join_points.get(symbol)
+
+    pub fn retain_top_level_thunks_for_module(&mut self, module_id: ModuleId) {
+        self.top_level_thunks
+            .retain(|s, _| s.module_id() == module_id);
     }
-    fn remove_join_point(&mut self, symbol: &JoinPointId) {
-        self.join_points.remove(symbol);
-    }
-    fn get_mut_join_point(&mut self, symbol: &JoinPointId) -> Option<&mut PhiValue<'ctx>> {
-        self.join_points.get_mut(symbol)
-    }
-    fn insert_join_point(&mut self, symbol: JoinPointId, value: PhiValue<'ctx>) {
-        self.join_points.insert(symbol, value);
-    }
-    */
 }
 
 pub struct Env<'a, 'ctx, 'env> {
@@ -1157,17 +1158,34 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
             list_literal(env, inplace, scope, elem_layout, elems)
         }
         FunctionPointer(symbol, layout) => {
-            let fn_name = layout_ids
-                .get(*symbol, layout)
-                .to_symbol_string(*symbol, &env.interns);
-            let ptr = env
-                .module
-                .get_function(fn_name.as_str())
-                .unwrap_or_else(|| panic!("Could not get pointer to unknown function {:?}", symbol))
-                .as_global_value()
-                .as_pointer_value();
+            match scope.top_level_thunks.get(symbol) {
+                Some((_layout, function_value)) => {
+                    // this is a 0-argument thunk, evaluate it!
+                    let call = env.builder.build_call(
+                        function_value.clone(),
+                        &[],
+                        "evaluate_top_level_thunk",
+                    );
 
-            BasicValueEnum::PointerValue(ptr)
+                    call.try_as_basic_value().left().unwrap()
+                }
+                None => {
+                    // this is a function pointer, store it
+                    let fn_name = layout_ids
+                        .get(*symbol, layout)
+                        .to_symbol_string(*symbol, &env.interns);
+                    let ptr = env
+                        .module
+                        .get_function(fn_name.as_str())
+                        .unwrap_or_else(|| {
+                            panic!("Could not get pointer to unknown function {:?}", symbol)
+                        })
+                        .as_global_value()
+                        .as_pointer_value();
+
+                    BasicValueEnum::PointerValue(ptr)
+                }
+            }
         }
         RuntimeErrorFunction(_) => todo!(),
     }
@@ -1847,6 +1865,7 @@ pub fn build_proc_header<'a, 'ctx, 'env>(
 pub fn build_proc<'a, 'ctx, 'env>(
     env: &'a Env<'a, 'ctx, 'env>,
     layout_ids: &mut LayoutIds<'a>,
+    mut scope: Scope<'a, 'ctx>,
     proc: roc_mono::ir::Proc<'a>,
     fn_val: FunctionValue<'ctx>,
 ) {
@@ -1859,8 +1878,6 @@ pub fn build_proc<'a, 'ctx, 'env>(
 
     builder.position_at_end(entry);
 
-    let mut scope = Scope::default();
-
     // Add args to scope
     for (arg_val, (layout, arg_symbol)) in fn_val.get_param_iter().zip(args) {
         set_name(arg_val, arg_symbol.ident_string(&env.interns));
diff --git a/compiler/gen/tests/gen_primitives.rs b/compiler/gen/tests/gen_primitives.rs
index 6a53c93974..23d2d6de10 100644
--- a/compiler/gen/tests/gen_primitives.rs
+++ b/compiler/gen/tests/gen_primitives.rs
@@ -529,7 +529,6 @@ mod gen_primitives {
     }
 
     #[test]
-    #[ignore]
     fn top_level_constant() {
         assert_evals_to!(
             indoc!(
diff --git a/compiler/gen/tests/helpers/eval.rs b/compiler/gen/tests/helpers/eval.rs
index 5377918cbb..ced5d6ab94 100644
--- a/compiler/gen/tests/helpers/eval.rs
+++ b/compiler/gen/tests/helpers/eval.rs
@@ -25,7 +25,7 @@ pub fn helper<'a>(
     inkwell::execution_engine::ExecutionEngine<'a>,
 ) {
     use inkwell::OptimizationLevel;
-    use roc_gen::llvm::build::{build_proc, build_proc_header};
+    use roc_gen::llvm::build::{build_proc, build_proc_header, Scope};
     use std::path::{Path, PathBuf};
 
     let stdlib_mode = stdlib.mode;
@@ -141,15 +141,29 @@ pub fn helper<'a>(
     // Add all the Proc headers to the module.
     // We have to do this in a separate pass first,
     // because their bodies may reference each other.
+    let mut scope = Scope::default();
     for ((symbol, layout), proc) in procedures.drain() {
         let fn_val = build_proc_header(&env, &mut layout_ids, symbol, &layout, &proc);
 
+        if proc.args.is_empty() {
+            // this is a 0-argument thunk, i.e. a top-level constant definition
+            // it must be in-scope everywhere in the module!
+            scope.insert_top_level_thunk(symbol, layout, fn_val);
+        }
+
         headers.push((proc, fn_val));
     }
 
     // Build each proc using its header info.
     for (proc, fn_val) in headers {
-        build_proc(&env, &mut layout_ids, proc, fn_val);
+        let mut current_scope = scope.clone();
+
+        // only have top-level thunks for this proc's module in scope
+        // this retain is not needed for correctness, but will cause less confusion when debugging
+        let home = proc.name.module_id();
+        current_scope.retain_top_level_thunks_for_module(home);
+
+        build_proc(&env, &mut layout_ids, scope.clone(), proc, fn_val);
 
         if fn_val.verify(true) {
             function_pass.run_on(&fn_val);
diff --git a/compiler/mono/src/ir.rs b/compiler/mono/src/ir.rs
index 4676341203..4346c69c7b 100644
--- a/compiler/mono/src/ir.rs
+++ b/compiler/mono/src/ir.rs
@@ -203,25 +203,23 @@ impl<'a> Procs<'a> {
         for (key, in_prog_proc) in self.specialized.into_iter() {
             match in_prog_proc {
                 InProgress => unreachable!("The procedure {:?} should have be done by now", key),
-                Done(proc) => {
+                Done(mut proc) => {
+                    use self::SelfRecursive::*;
+                    if let SelfRecursive(id) = proc.is_self_recursive {
+                        proc.body = crate::tail_recursion::make_tail_recursive(
+                            arena,
+                            id,
+                            proc.name,
+                            proc.body.clone(),
+                            proc.args,
+                        );
+                    }
+
                     result.insert(key, proc);
                 }
             }
         }
 
-        for (_, proc) in result.iter_mut() {
-            use self::SelfRecursive::*;
-            if let SelfRecursive(id) = proc.is_self_recursive {
-                proc.body = crate::tail_recursion::make_tail_recursive(
-                    arena,
-                    id,
-                    proc.name,
-                    proc.body.clone(),
-                    proc.args,
-                );
-            }
-        }
-
         result
     }