diff --git a/src/protocol/mod.rs b/src/protocol/mod.rs
index 11a19bd3ffbdc35734f7290fdbe9bad6d3276054..9a41b28c25581af0f1467043b1f9c21082f5e794 100644
--- a/src/protocol/mod.rs
+++ b/src/protocol/mod.rs
@@ -94,20 +94,20 @@ impl ProtocolDescription {
         let definition_id = definition_id.unwrap();
 
         let ast_definition = &self.heap[definition_id];
-        if !ast_definition.is_component() {
+        if !ast_definition.is_procedure() {
             return Err(ComponentCreationError::DefinitionNotComponent);
         }
 
         // Make sure that the types of the provided value group matches that of
         // the expected types.
-        let ast_definition = ast_definition.as_component();
-        if !ast_definition.poly_vars.is_empty() {
+        let ast_definition = ast_definition.as_procedure();
+        if !ast_definition.poly_vars.is_empty() || ast_definition.kind == ProcedureKind::Function {
             return Err(ComponentCreationError::DefinitionNotComponent);
         }
 
         // - check number of arguments by retrieving the one instantiated
         //   monomorph
-        let concrete_type = ConcreteType{ parts: vec![ConcreteTypePart::Component(definition_id, 0)] };
+        let concrete_type = ConcreteType{ parts: vec![ConcreteTypePart::Component(ast_definition.this, 0)] };
         let mono_index = self.types.get_procedure_monomorph_type_id(&definition_id, &concrete_type.parts).unwrap();
         let mono_type = self.types.get_procedure_monomorph(mono_index);
         if mono_type.arg_types.len() != arguments.values.len() {
@@ -125,7 +125,7 @@ impl ProtocolDescription {
 
         // By now we're sure that all of the arguments are correct. So create
         // the connector.
-        return Ok(Prompt::new(&self.types, &self.heap, definition_id, mono_index, arguments));
+        return Ok(Prompt::new(&self.types, &self.heap, ast_definition.this, mono_index, arguments));
     }
 
     fn lookup_module_root(&self, module_name: &[u8]) -> Option<RootId> {