diff --git a/include/Stk.h b/include/Stk.h
index 8e3f709..5c9c37b 100644
--- a/include/Stk.h
+++ b/include/Stk.h
@@ -236,7 +236,7 @@ protected:
   void removeSampleRateAlert( Stk *ptr );
 
   //! Internal function for error reporting that assumes message in \c oStream_ variable.
-  void handleError( StkError::Type type );
+  void handleError( StkError::Type type ) const;
 };
 
 
diff --git a/src/Stk.cpp b/src/Stk.cpp
index ab90da9..97a4ecd 100644
--- a/src/Stk.cpp
+++ b/src/Stk.cpp
@@ -192,7 +192,7 @@ void Stk :: sleep(unsigned long milliseconds)
 #endif
 }
 
-void Stk :: handleError( StkError::Type type )
+void Stk :: handleError( StkError::Type type ) const
 {
   handleError( oStream_.str(), type );
   oStream_.str( std::string() ); // reset the ostringstream buffer