diff --git a/runtime/vm/runtime_entry.cc b/runtime/vm/runtime_entry.cc
index 95542e0..e5db6fa 100644
--- a/runtime/vm/runtime_entry.cc
+++ b/runtime/vm/runtime_entry.cc
@@ -637,18 +637,24 @@
     }
     return;
   }
+  Class& instance_class = Class::Handle(zone);
   if (instance.IsSmi()) {
-    if (FLAG_trace_type_checks) {
-      OS::PrintErr("UpdateTypeTestCache: instance is Smi\n");
+    if (FLAG_enable_interpreter) {
+      instance_class = Smi::Class();
+    } else {
+      if (FLAG_trace_type_checks) {
+        OS::PrintErr("UpdateTypeTestCache: instance is Smi, not updating\n");
+      }
+      return;
     }
-    return;
+  } else {
+    instance_class = instance.clazz();
   }
   // If the type is uninstantiated and refers to parent function type
   // parameters, the function_type_arguments have been canonicalized
   // when concatenated.
   ASSERT(function_type_arguments.IsNull() ||
          function_type_arguments.IsCanonical());
-  const Class& instance_class = Class::Handle(zone, instance.clazz());
   auto& instance_class_id_or_function = Object::Handle(zone);
   auto& instance_type_arguments = TypeArguments::Handle(zone);
   auto& instance_parent_function_type_arguments = TypeArguments::Handle(zone);