diff --git a/msg-center-api/src/main/java/cn/axzo/msg/center/service/pending/ModelVersion.java b/msg-center-api/src/main/java/cn/axzo/msg/center/service/pending/ModelVersion.java
index d5292a9a..f72ebf0e 100644
--- a/msg-center-api/src/main/java/cn/axzo/msg/center/service/pending/ModelVersion.java
+++ b/msg-center-api/src/main/java/cn/axzo/msg/center/service/pending/ModelVersion.java
@@ -1,7 +1,6 @@
 package cn.axzo.msg.center.service.pending;
 
 import cn.axzo.framework.domain.ServiceException;
-import com.microsoft.schemas.office.x2006.encryption.STSaltSize;
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.RequiredArgsConstructor;
@@ -19,6 +18,7 @@ public class ModelVersion {
 
     private static final Map<Integer, ModelVersion> VERSIONS = new ConcurrentHashMap<>();
     private static final Integer MAX_VERSION_NUMBER = 500;
+    private static final Integer MIN_VERSION_NUMBER = -1;
 
     public static final ModelVersion V2 = of(null);
     public static final ModelVersion V3 = of(3);
@@ -28,9 +28,7 @@ public class ModelVersion {
 
     public static ModelVersion of(Integer version) {
         // attack?
-        if (version != null
-                && version > MAX_VERSION_NUMBER
-                && version < Integer.MAX_VALUE)
+        if (version != null && (version > MAX_VERSION_NUMBER || version < MIN_VERSION_NUMBER))
             throw new ServiceException("model version is too large");
         if (version == null) version = Integer.MIN_VALUE;
         return VERSIONS.computeIfAbsent(version, ModelVersion::new);