diff --git a/honoka/plugins/wordsdic.cpp b/honoka/plugins/wordsdic.cpp
index 2af1a0d..ed2f4d8 100644
--- a/honoka/plugins/wordsdic.cpp
+++ b/honoka/plugins/wordsdic.cpp
@@ -56,9 +56,9 @@
 /*!
     \fn Honoka::WordsDic::find(const string &word)
  */
-vector<string> Honoka::WordsDic::find(const string &word)
+set<string> Honoka::WordsDic::find(const string &word)
 {
-    vector<string> res,bres;
+    set<string> res,bres;
     if (fd == -1) return res;
     if (word.length() > 255) return res;
     if (fd == -1) return res;
@@ -83,12 +83,12 @@
                 s += p[i];
             }
             if (strncmp(ow,ob,word.length()) == 0)
-                res.push_back(s);
-            else bres.push_back(s);
+                res.insert(s);
+            else bres.insert(s);
         }
         while(*p != '\n') p ++;
         p ++;
     }
-    for(unsigned int i = 0;i < bres.size();i ++) res.push_back(bres[i]);
+    for(set<string>::iterator it = bres.begin();it != bres.end();it ++) res.insert(*it);
     return res;
 }
diff --git a/honoka/plugins/wordsdic.h b/honoka/plugins/wordsdic.h
index 12df5c6..a911ded 100644
--- a/honoka/plugins/wordsdic.h
+++ b/honoka/plugins/wordsdic.h
@@ -24,7 +24,7 @@
 #include <cstdio>
 #include <cstdlib>
 #include <string>
-#include <vector>
+#include <set>
 
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -42,7 +42,7 @@
     WordsDic(const string &filename);
 
     ~WordsDic();
-    vector<string> find(const string &word);
+    set<string> find(const string &word);
 
 protected:
     int fd;
diff --git a/honoka/plugins/wordsprediction.cpp b/honoka/plugins/wordsprediction.cpp
index e766ca6..119baf8 100644
--- a/honoka/plugins/wordsprediction.cpp
+++ b/honoka/plugins/wordsprediction.cpp
@@ -72,7 +72,7 @@
     if (!word.length()) return l;
     prewords = str.substr(0,str.length() - word.length());
     pos = prewords.length();
-    vector<string> res = dic->find(utf8_wcstombs(word).c_str());
+    set<string> res = dic->find(utf8_wcstombs(word).c_str());
     if (res.size() > limit) {
         l.Title = utf8_mbstowcs(String(_("too many prediction results!")));
         l.kType = PREDICTION;
@@ -84,7 +84,7 @@
     } else {
         l.Title = utf8_mbstowcs(String(_("lookup result")));
         l.kType = PREDICTION;
-        for(vector<string>::iterator it = res.begin();it != res.end();it ++) {
+        for(set<string>::iterator it = res.begin();it != res.end();it ++) {
             if (addSpace) l.kouho.push_back(ResultEntry(prewords + utf8_mbstowcs(*it) + utf8_mbstowcs(" "),utf8_mbstowcs(*it)));
             else l.kouho.push_back(ResultEntry(prewords + utf8_mbstowcs(*it),utf8_mbstowcs(*it)));
         }