diff --git a/cli/src/repl/gen.rs b/cli/src/repl/gen.rs
index 1d9427842a..be27087b38 100644
--- a/cli/src/repl/gen.rs
+++ b/cli/src/repl/gen.rs
@@ -131,11 +131,15 @@ pub fn gen_and_eval(src: &[u8], target: Triple, opt_level: OptLevel) -> Result<R
         let content = subs.get(main_fn_var).content;
         let expr_type_str = content_to_string(content.clone(), &subs, home, &interns);
 
-        let (_, main_fn_layout) = procedures
-            .keys()
-            .find(|(s, _)| *s == main_fn_symbol)
-            .unwrap()
-            .clone();
+        let (_, main_fn_layout) = match procedures.keys().find(|(s, _)| *s == main_fn_symbol) {
+            Some(layout) => layout.clone(),
+            None => {
+                return Ok(ReplOutput::NoProblems {
+                    expr: "<function>".to_string(),
+                    expr_type: expr_type_str,
+                });
+            }
+        };
 
         let ptr_bytes = target.pointer_width().unwrap().bytes() as u32;
 
diff --git a/compiler/load/src/file.rs b/compiler/load/src/file.rs
index fd61954feb..1425b8b921 100644
--- a/compiler/load/src/file.rs
+++ b/compiler/load/src/file.rs
@@ -20,7 +20,7 @@ use roc_module::symbol::{
 use roc_mono::ir::{
     CapturedSymbols, ExternalSpecializations, PartialProc, PendingSpecialization, Proc, Procs,
 };
-use roc_mono::layout::{Layout, LayoutCache};
+use roc_mono::layout::{Layout, LayoutCache, LayoutProblem};
 use roc_parse::ast::{self, Attempting, StrLiteral, TypeAnnotation};
 use roc_parse::header::{
     ExposesEntry, ImportsEntry, PackageEntry, PackageOrPath, PlatformHeader, To, TypedIdent,
@@ -3503,9 +3503,20 @@ fn add_def_to_module<'a>(
                             mono_env.subs,
                         ) {
                             Ok(l) => l,
-                            Err(err) => {
-                                // a host-exposed function is not monomorphized
-                                todo!("The host-exposed function {:?} does not have a valid layout (e.g. maybe the function wasn't monomorphic): {:?}", symbol, err)
+                            Err(LayoutProblem::Erroneous) => {
+                                let message = "top level function has erroneous type";
+                                procs.runtime_errors.insert(symbol, message);
+                                return;
+                            }
+                            Err(LayoutProblem::UnresolvedTypeVar(v)) => {
+                                let message = format!(
+                                    "top level function has unresolved type variable {:?}",
+                                    v
+                                );
+                                procs
+                                    .runtime_errors
+                                    .insert(symbol, mono_env.arena.alloc(message));
+                                return;
                             }
                         };
 
diff --git a/compiler/mono/src/ir.rs b/compiler/mono/src/ir.rs
index dc08c98176..f5e2f0b0ca 100644
--- a/compiler/mono/src/ir.rs
+++ b/compiler/mono/src/ir.rs
@@ -1508,7 +1508,6 @@ pub fn specialize_all<'a>(
                         ));
 
                         procs.runtime_errors.insert(name, error_msg);
-                        panic!("failed to specialize {:?}", name);
                     }
                 }
             }