diff --git a/src/cst/module_declaration.rs b/src/cst/module_declaration.rs
index a2627a8..8369040 100644
--- a/src/cst/module_declaration.rs
+++ b/src/cst/module_declaration.rs
@@ -314,7 +314,8 @@ impl<'a> ModuleDeclaration {
                 let mut builder = UnitContext::builder(&mut context.unit_ctx.data);
                 let ext_unit =
                     builder.add_extern(ext_entity.name().clone(), ext_entity.sig().clone());
-                builder.ins().inst(ext_unit, inputs, outputs);
+                let inst = builder.ins().inst(ext_unit, inputs, outputs);
+                context.syntax_table.insert_inst(builder.unit(), inst, json);
             } else {
                 error!("module '{}' not found", name);
             }