diff --git a/target-alpha/cpu.c b/target-alpha/cpu.c
index 3ac0fde..0d6975e 100644
--- a/target-alpha/cpu.c
+++ b/target-alpha/cpu.c
@@ -96,7 +96,7 @@ static ObjectClass *alpha_cpu_class_by_name(const char *cpu_model)
     }
 
     oc = object_class_by_name(cpu_model);
-    if (oc != NULL) {
+    if (oc != NULL && object_class_dynamic_cast(oc, TYPE_ALPHA_CPU) != NULL) {
         return oc;
     }