diff --git a/src/Segment.cpp b/src/Segment.cpp
index 5a38017..2c3b666 100644
--- a/src/Segment.cpp
+++ b/src/Segment.cpp
@@ -64,7 +64,7 @@ namespace CppJieba
 		
 		return true;
 	}
-	bool Segment::extract(const string& utf8Str, vector<string>& keywords)
+	bool Segment::extract(const string& utf8Str, vector<string>& keywords, uint topN)
 	{
 		LogInfo(utf8Str);
 		bool retFlag;
@@ -86,7 +86,7 @@ namespace CppJieba
 		}
 		LogDebug(string_format("_filter res:[%s]", joinStr(tmp, ",").c_str()));
 
-		retFlag = _extractTopN(tmp, keywords, 5);
+		retFlag = _extractTopN(tmp, keywords, topN);
 		if(!retFlag)
 		{
 			LogError("_extractTopN failed.");
diff --git a/src/Segment.h b/src/Segment.h
index 7a74bb7..7f73b77 100644
--- a/src/Segment.h
+++ b/src/Segment.h
@@ -20,7 +20,7 @@ namespace CppJieba
 			bool destroy();
 		public:
 			bool cutDAG(const string& chStr, vector<string>& res);
-			bool extract(const string& utf8Str, vector<string>& keywords);
+			bool extract(const string& utf8Str, vector<string>& keywords, uint topN);
 			double getUtf8WordWeight(const string& word);
 			double getUniWordWeight(const string& word);