diff --git a/lib/tokenlist.cpp b/lib/tokenlist.cpp
index 59f0a0fe4..57ab2033b 100644
--- a/lib/tokenlist.cpp
+++ b/lib/tokenlist.cpp
@@ -353,7 +353,7 @@ bool TokenList::createTokens(std::istream &code, const std::string& file0)
 
 //---------------------------------------------------------------------------
 
-void TokenList::createAst()
+void TokenList::createAst() const
 {
     // operators that must be ordered according to C-precedence
     const char * const operators[] = {
diff --git a/lib/tokenlist.h b/lib/tokenlist.h
index f3f26da1f..a442fda2d 100644
--- a/lib/tokenlist.h
+++ b/lib/tokenlist.h
@@ -105,7 +105,7 @@ public:
      */
     std::string fileLine(const Token *tok) const;
 
-    void createAst();
+    void createAst() const;
 
 private:
     /** Disable copy constructor, no implementation */