diff --git a/commons-serialize-generator/src/main/java/io/gitlab/jfronny/commons/serialize/generator/SerializeGeneratorProcessor.java b/commons-serialize-generator/src/main/java/io/gitlab/jfronny/commons/serialize/generator/SerializeGeneratorProcessor.java
index 83dfcfa..94e6903 100644
--- a/commons-serialize-generator/src/main/java/io/gitlab/jfronny/commons/serialize/generator/SerializeGeneratorProcessor.java
+++ b/commons-serialize-generator/src/main/java/io/gitlab/jfronny/commons/serialize/generator/SerializeGeneratorProcessor.java
@@ -114,7 +114,8 @@ public class SerializeGeneratorProcessor extends AbstractProcessor2 {
                                 switch (name) {
                                     case "adapter" -> {
                                         if (bld.adapter != null) throw new IllegalArgumentException("Duplicate annotation parameter: adapter");
-                                        bld.adapter = (TypeMirror) value.getValue();
+                                        if (value.getValue() instanceof TypeMirror tm) bld.adapter = tm;
+                                        else throw new IllegalArgumentException("Unexpected value type: " + value.getValue().getClass() + " (with value" + value.getValue() + ")");
                                     }
                                     case "nullSafe" -> {
                                         if (bld.nullSafe != null) throw new IllegalArgumentException("Duplicate annotation parameter: nullSafe");