diff --git a/ChangeLog.md b/ChangeLog.md
index f289fb4..23d5193 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,6 +1,11 @@
 # CppJieba ChangeLog
 
-# v4.0.0
+## next version
+
+1. QuerySegment切词时加一层判断，当长词满足IsAllAscii(比如英文单词)时，不进行细粒度分词。
+2. QuerySegment新增SetMaxWordLen和GetMaxWordLen接口。
+
+## v4.0.0
 
 1. 支持多个userdict载入，多词典路径用英文冒号(:)作为分隔符，就当是向环境变量PATH致敬，哈哈。
 2. userdict是不带权重的，之前对于新的userword默认设置词频权重为最大值，现已支持可配置，默认使用中位值。
diff --git a/src/QuerySegment.hpp b/src/QuerySegment.hpp
index 354574b..56083d2 100644
--- a/src/QuerySegment.hpp
+++ b/src/QuerySegment.hpp
@@ -45,7 +45,7 @@ class QuerySegment: public SegmentBase {
     vector<Unicode> fullRes;
     for (vector<Unicode>::const_iterator mixResItr = mixRes.begin(); mixResItr != mixRes.end(); mixResItr++) {
       // if it's too long, Cut with fullSeg_, put fullRes in res
-      if (mixResItr->size() > maxWordLen_) {
+      if (mixResItr->size() > maxWordLen_ && !IsAllAscii(*mixResItr)) {
         fullSeg_.Cut(mixResItr->begin(), mixResItr->end(), fullRes);
         for (vector<Unicode>::const_iterator fullResItr = fullRes.begin(); fullResItr != fullRes.end(); fullResItr++) {
           res.push_back(*fullResItr);
@@ -58,12 +58,26 @@ class QuerySegment: public SegmentBase {
       }
     }
   }
+  void SetMaxWordLen(size_t len) {
+    maxWordLen_ = len;
+  }
+  size_t GetMaxWordLen() const {
+    return maxWordLen_;
+  }
  private:
+  bool IsAllAscii(const Unicode& s) const {
+   for(size_t i = 0; i < s.size(); i++) {
+     if (s[i] >= 0x80) {
+       return false;
+     }
+   }
+   return true;
+  }
   MixSegment mixSeg_;
   FullSegment fullSeg_;
   size_t maxWordLen_;
+}; // QuerySegment
 
-};
-}
+} // namespace cppjieba
 
 #endif
diff --git a/test/testdata/userdict.english b/test/testdata/userdict.english
new file mode 100644
index 0000000..b0784a4
--- /dev/null
+++ b/test/testdata/userdict.english
@@ -0,0 +1,2 @@
+in
+internal
diff --git a/test/unittest/segments_test.cpp b/test/unittest/segments_test.cpp
index cacae35..0c6b3ce 100644
--- a/test/unittest/segments_test.cpp
+++ b/test/unittest/segments_test.cpp
@@ -225,7 +225,7 @@ TEST(QuerySegment, Test1) {
 }
 
 TEST(QuerySegment, Test2) {
-  QuerySegment segment("../test/testdata/extra_dict/jieba.dict.small.utf8", "../dict/hmm_model.utf8", "../test/testdata/userdict.utf8", 3);
+  QuerySegment segment("../test/testdata/extra_dict/jieba.dict.small.utf8", "../dict/hmm_model.utf8", "../test/testdata/userdict.utf8:../test/testdata/userdict.english", 3);
 
   {
     const char* str = "小明硕士毕业于中国科学院计算所，后在日本京都大学深造";
@@ -251,6 +251,21 @@ TEST(QuerySegment, Test2) {
     ASSERT_EQ(s1, s2);
   }
 
+  {
+    vector<string> words;
+    segment.Cut("internal", words);
+    string s = join(words.begin(), words.end(), "/");
+    ASSERT_EQ("internal", s);
+  }
+
+  segment.SetMaxWordLen(5);
+
+  {
+    vector<string> words;
+    segment.Cut("中国科学院", words);
+    string s = join(words.begin(), words.end(), "/");
+    ASSERT_EQ("中国科学院", s);
+  }
 }
 
 TEST(LevelSegmentTest, Test0) {