diff --git a/lib/tokenlist.cpp b/lib/tokenlist.cpp
index 759cffd03..c5ccdc73a 100644
--- a/lib/tokenlist.cpp
+++ b/lib/tokenlist.cpp
@@ -60,20 +60,6 @@ const std::string& TokenList::getSourceFilePath() const
     return getFiles()[0];
 }
 
-bool TokenList::isC() const
-{
-    if (!_settings)
-        return Path::isC(getSourceFilePath());
-    return _settings->enforcedLang == Settings::C || (_settings->enforcedLang == Settings::None && Path::isC(getSourceFilePath()));
-}
-
-bool TokenList::isCPP() const
-{
-    if (!_settings)
-        return Path::isCPP(getSourceFilePath());
-    return _settings->enforcedLang == Settings::CPP || (_settings->enforcedLang == Settings::None && Path::isCPP(getSourceFilePath()));
-}
-
 //---------------------------------------------------------------------------
 
 // Deallocate lists..
@@ -94,6 +80,17 @@ unsigned int TokenList::appendFileIfNew(const std::string &fileName)
 
     // The "_files" vector remembers what files have been tokenized..
     _files.push_back(Path::simplifyPath(fileName));
+
+    // Update _isC and _isCPP properties
+    if (_files.size() == 1) { // Update only useful if first file added to _files
+        if (!_settings) {
+            _isC = Path::isC(getSourceFilePath());
+            _isCPP = Path::isCPP(getSourceFilePath());
+        } else {
+            _isC = _settings->enforcedLang == Settings::C || (_settings->enforcedLang == Settings::None && Path::isC(getSourceFilePath()));
+            _isCPP = _settings->enforcedLang == Settings::CPP || (_settings->enforcedLang == Settings::None && Path::isCPP(getSourceFilePath()));
+        }
+    }
     return static_cast<unsigned int>(_files.size() - 1);
 }
 
@@ -210,7 +207,7 @@ void TokenList::insertTokens(Token *dest, const Token *src, unsigned int n)
 
 bool TokenList::createTokens(std::istream &code, const std::string& file0)
 {
-    _files.push_back(file0);
+    appendFileIfNew(file0);
 
     // line number in parsed code
     unsigned int lineno = 1;
diff --git a/lib/tokenlist.h b/lib/tokenlist.h
index 3134c7c8c..69f283240 100644
--- a/lib/tokenlist.h
+++ b/lib/tokenlist.h
@@ -44,10 +44,14 @@ public:
     const std::string& getSourceFilePath() const;
 
     /** Is the code C. Used for bailouts */
-    bool isC() const;
+    bool isC() const {
+        return _isC;
+    }
 
     /** Is the code CPP. Used for bailouts */
-    bool isCPP() const;
+    bool isCPP() const {
+        return _isCPP;
+    }
 
     /**
      * Delete all tokens in given token list
@@ -136,6 +140,9 @@ private: /// private
 
     /** settings */
     const Settings* _settings;
+
+    /** File is known to be C/C++ code */
+    bool _isC, _isCPP;
 };
 
 /// @}