diff --git a/nac3core/src/codegen/test.rs b/nac3core/src/codegen/test.rs
index 4e63fd30..b3963d87 100644
--- a/nac3core/src/codegen/test.rs
+++ b/nac3core/src/codegen/test.rs
@@ -46,8 +46,8 @@ impl SymbolResolver for Resolver {
         _: &[Arc<RwLock<TopLevelDef>>],
         _: &PrimitiveStore,
         str: StrRef,
-    ) -> Option<Type> {
-        self.id_to_type.get(&str).cloned()
+    ) -> Result<Type, String> {
+        self.id_to_type.get(&str).cloned().ok_or_else(|| format!("cannot find symbol `{}`", str))
     }
 
     fn get_symbol_value<'ctx, 'a>(
diff --git a/nac3core/src/toplevel/test.rs b/nac3core/src/toplevel/test.rs
index 1aef5771..0fb36ab1 100644
--- a/nac3core/src/toplevel/test.rs
+++ b/nac3core/src/toplevel/test.rs
@@ -45,9 +45,13 @@ impl SymbolResolver for Resolver {
         _: &[Arc<RwLock<TopLevelDef>>],
         _: &PrimitiveStore,
         str: StrRef,
-    ) -> Option<Type> {
-        let ret = self.0.id_to_type.lock().get(&str).cloned();
-        ret
+    ) -> Result<Type, String> {
+        self.0
+            .id_to_type
+            .lock()
+            .get(&str)
+            .cloned()
+            .ok_or_else(|| format!("cannot find symbol `{}`", str))
     }
 
     fn get_symbol_value<'ctx, 'a>(
diff --git a/nac3core/src/typecheck/type_inferencer/test.rs b/nac3core/src/typecheck/type_inferencer/test.rs
index 0d1492ca..b4633064 100644
--- a/nac3core/src/typecheck/type_inferencer/test.rs
+++ b/nac3core/src/typecheck/type_inferencer/test.rs
@@ -29,8 +29,8 @@ impl SymbolResolver for Resolver {
         _: &[Arc<RwLock<TopLevelDef>>],
         _: &PrimitiveStore,
         str: StrRef,
-    ) -> Option<Type> {
-        self.id_to_type.get(&str).cloned()
+    ) -> Result<Type, String> {
+        self.id_to_type.get(&str).cloned().ok_or_else(|| format!("cannot find symbol `{}`", str))
     }
 
     fn get_symbol_value<'ctx, 'a>(