diff --git a/Source/Engine/McBopomofoLM.cpp b/Source/Engine/McBopomofoLM.cpp
index b7bfd1b5..0ffdaddd 100644
--- a/Source/Engine/McBopomofoLM.cpp
+++ b/Source/Engine/McBopomofoLM.cpp
@@ -18,17 +18,23 @@ McBopomofoLM::~McBopomofoLM()
 
 void McBopomofoLM::loadLanguageModel(const char* languageModelDataPath)
 {
-    m_languageModel.close();
-    m_languageModel.open(languageModelDataPath);
+    if (languageModelDataPath) {
+        m_languageModel.close();
+        m_languageModel.open(languageModelDataPath);
+    }
 }
 
 void McBopomofoLM::loadUserPhrases(const char* userPhrasesDataPath,
                                    const char* excludedPhrasesDataPath)
 {
-    m_userPhrases.close();
-    m_userPhrases.open(userPhrasesDataPath);
-    m_excludedPhrases.close();
-    m_excludedPhrases.open(excludedPhrasesDataPath);
+    if (userPhrasesDataPath) {
+        m_userPhrases.close();
+        m_userPhrases.open(userPhrasesDataPath);
+    }
+    if (excludedPhrasesDataPath) {
+        m_excludedPhrases.close();
+        m_excludedPhrases.open(excludedPhrasesDataPath);
+    }
 }
 
 const vector<Bigram> McBopomofoLM::bigramsForKeys(const string& preceedingKey, const string& key)
diff --git a/Source/LanguageModelManager.mm b/Source/LanguageModelManager.mm
index ba632b67..0af6d6eb 100644
--- a/Source/LanguageModelManager.mm
+++ b/Source/LanguageModelManager.mm
@@ -35,7 +35,7 @@ static void LTLoadLanguageModelFile(NSString *filenameWithoutExtension, McBopomo
 + (void)loadUserPhrasesModel
 {
     gLanguageModelMcBopomofo.loadUserPhrases([[self userPhrasesDataPathMcBopomofo] UTF8String], [[self excludedPhrasesDataPathMcBopomofo] UTF8String]);
-    gLanguageModelPlainBopomofo.loadUserPhrases("", [[self excludedPhrasesDataPathPlainBopomofo] UTF8String]);
+    gLanguageModelPlainBopomofo.loadUserPhrases(NULL, [[self excludedPhrasesDataPathPlainBopomofo] UTF8String]);
 }
 
 + (BOOL)checkIfUserDataFolderExists
diff --git a/Source/McBopomofo-Bridging-Header.h b/Source/McBopomofo-Bridging-Header.h
index 6e2a1a13..51d288b9 100644
--- a/Source/McBopomofo-Bridging-Header.h
+++ b/Source/McBopomofo-Bridging-Header.h
@@ -2,9 +2,6 @@
 //  Use this file to import your target's public headers that you would like to expose to Swift.
 //
 
-//extern void LTLoadLanguageModel(void);
-//extern void LTLoadUserLanguageModelFile(void);
-
 @import Foundation;
 
 @interface LanguageModelManager : NSObject