diff --git a/include/osg/Math b/include/osg/Math
index 4ecc20a03..1e3ce7c7c 100644
--- a/include/osg/Math
+++ b/include/osg/Math
@@ -196,8 +196,13 @@ inline double round(double v) { return v>=0.0?floor(v+0.5):ceil(v-0.5); }
 #else
     #if defined(__APPLE__)
         #if !defined (APPLE_PRE_10_2)
-            inline bool isNaN(float v) { return isnan(v); }
-            inline bool isNaN(double v) { return isnan(v); }
+            #if __GNUC__ >= 4
+                inline bool isNaN(float v) { return isnan(v); }
+                inline bool isNaN(double v) { return isnan(v); }
+            #else
+                inline bool isNaN(float v) { return std::isnan(v); }
+                inline bool isNaN(double v) { return std::isnan(v); }
+            #endif
         #else
             inline bool isNaN(float v) { return std::isnan(v); }
             inline bool isNaN(double v) { return std::isnan(v); }