diff --git a/include/osg/Timer b/include/osg/Timer
index cd167cd01..37f52b4d9 100644
--- a/include/osg/Timer
+++ b/include/osg/Timer
@@ -36,9 +36,9 @@ class SG_EXPORT Timer {
 	#if defined __DARWIN_OSX__  || defined macintosh
 	// PJA MAC OSX - inline Tick() pollutes namespace so badly 
 	// we cant compile, due to Carbon.h ...
-        Timer_t tick();
+        Timer_t tick() const;
 	#else
-		inline Timer_t tick();
+		inline Timer_t tick() const;
 	#endif
 		
         inline double delta_s( Timer_t t1, Timer_t t2 ) const { return (double)(t2 - t1)*_secsPerClick; }
@@ -67,7 +67,7 @@ class SG_EXPORT Timer {
 
 namespace osg{
 
-    inline Timer_t Timer::tick( void )
+    inline Timer_t Timer::tick( void ) const
     {
         if (_useStandardClock) return clock();
         
@@ -100,7 +100,7 @@ namespace osg{
 
 namespace osg{
 
-    inline Timer_t Timer::tick()
+    inline Timer_t Timer::tick() const
     {
         if (_useStandardClock)
         {
@@ -122,7 +122,7 @@ namespace osg{
 
 namespace osg{
 
-    inline  Timer_t Timer::tick()
+    inline  Timer_t Timer::tick()  const
     {
         if (_useStandardClock)
         {
@@ -142,7 +142,7 @@ namespace osg{
     #include <sys/time.h>
 
 namespace osg{
-    inline  Timer_t Timer::tick()
+    inline  Timer_t Timer::tick() const
     {
         struct timeval tv;
         gettimeofday(&tv, NULL);
@@ -156,7 +156,7 @@ namespace osg{
 
 namespace osg{
 
-    inline  Timer_t Timer::tick( void ) { return std::clock(); }
+    inline  Timer_t Timer::tick( void ) const { return std::clock(); }
 };
 
 #endif
diff --git a/src/osg/Timer.cpp b/src/osg/Timer.cpp
index 7832d81a8..b6d7a1044 100644
--- a/src/osg/Timer.cpp
+++ b/src/osg/Timer.cpp
@@ -197,29 +197,31 @@ using namespace osg;
         }
 
     }
+
 #elif defined (__DARWIN_OSX__)  || defined (macintosh)
 
-#if defined (__DARWIN_OSX__)
-	#include <Carbon/Carbon.h>         // do I really have to link against the Carbon framework just for this?
-#else	
-	#include <MacTypes.h>
-	#include <Timer.h>
-#endif
+    #if defined (__DARWIN_OSX__)
+	    #include <Carbon/Carbon.h>         // do I really have to link against the Carbon framework just for this?
+    #else	
+	    #include <MacTypes.h>
+	    #include <Timer.h>
+    #endif
 
-Timer_t Timer::tick(void)
-{
-	UnsignedWide usecs;
-	Microseconds(&usecs);
-	
-	return (usecs.hi * 4294967296.0) + usecs.lo;
-}
 
-Timer::Timer( void )
-{
-	_useStandardClock = false;
-	_secsPerClick = 1e-6; // Carbon timer's precision.
+    Timer::Timer( void )
+    {
+	    _useStandardClock = false;
+	    _secsPerClick = 1e-6; // Carbon timer's precision.
 
-}
+    }
+
+    Timer_t Timer::tick(void) const
+    {
+	    UnsignedWide usecs;
+	    Microseconds(&usecs);
+
+	    return (usecs.hi * 4294967296.0) + usecs.lo;
+    }
 
 #elif defined(unix)