diff --git a/cli/src/repl/gen.rs b/cli/src/repl/gen.rs
index f36672a455..775345182f 100644
--- a/cli/src/repl/gen.rs
+++ b/cli/src/repl/gen.rs
@@ -2,6 +2,7 @@ use crate::repl::eval;
 use bumpalo::Bump;
 use inkwell::context::Context;
 use roc_build::link::module_to_dylib;
+use roc_build::program::FunctionIterator;
 use roc_collections::all::{MutMap, MutSet};
 use roc_fmt::annotation::Formattable;
 use roc_fmt::annotation::{Newlines, Parens};
@@ -111,6 +112,15 @@ pub fn gen_and_eval(src: &[u8], target: Triple, opt_level: OptLevel) -> Result<R
         let module = arena.alloc(roc_gen::llvm::build::module_from_builtins(&context, "app"));
         let builder = context.create_builder();
 
+        // mark our zig-defined builtins as internal
+        use inkwell::module::Linkage;
+        for function in FunctionIterator::from_module(module) {
+            let name = function.get_name().to_str().unwrap();
+            if name.starts_with("roc_builtins") {
+                function.set_linkage(Linkage::Internal);
+            }
+        }
+
         debug_assert_eq!(exposed_to_host.len(), 1);
         let (main_fn_symbol, main_fn_var) = exposed_to_host.iter().next().unwrap();
         let main_fn_symbol = *main_fn_symbol;
diff --git a/compiler/build/src/program.rs b/compiler/build/src/program.rs
index 8b5537be97..29ea54e98f 100644
--- a/compiler/build/src/program.rs
+++ b/compiler/build/src/program.rs
@@ -170,12 +170,12 @@ pub fn gen_from_mono_module(
         .expect("Writing .o file failed");
 }
 
-struct FunctionIterator<'ctx> {
+pub struct FunctionIterator<'ctx> {
     next: Option<FunctionValue<'ctx>>,
 }
 
 impl<'ctx> FunctionIterator<'ctx> {
-    fn from_module(module: &inkwell::module::Module<'ctx>) -> Self {
+    pub fn from_module(module: &inkwell::module::Module<'ctx>) -> Self {
         Self {
             next: module.get_first_function(),
         }
diff --git a/compiler/gen/tests/helpers/eval.rs b/compiler/gen/tests/helpers/eval.rs
index 95959224dd..bbe6888c78 100644
--- a/compiler/gen/tests/helpers/eval.rs
+++ b/compiler/gen/tests/helpers/eval.rs
@@ -1,5 +1,6 @@
 use libloading::Library;
 use roc_build::link::module_to_dylib;
+use roc_build::program::FunctionIterator;
 use roc_collections::all::{MutMap, MutSet};
 
 fn promote_expr_to_module(src: &str) -> String {
@@ -154,6 +155,15 @@ pub fn helper<'a>(
 
     let (dibuilder, compile_unit) = roc_gen::llvm::build::Env::new_debug_info(module);
 
+    // mark our zig-defined builtins as internal
+    use inkwell::module::Linkage;
+    for function in FunctionIterator::from_module(module) {
+        let name = function.get_name().to_str().unwrap();
+        if name.starts_with("roc_builtins") {
+            function.set_linkage(Linkage::Internal);
+        }
+    }
+
     // Compile and add all the Procs before adding main
     let env = roc_gen::llvm::build::Env {
         arena: &arena,