diff --git a/include/wx/math.h b/include/wx/math.h
index de561737dd..f1f4d889f7 100644
--- a/include/wx/math.h
+++ b/include/wx/math.h
@@ -105,9 +105,6 @@
 
     inline bool wxIsNullDouble(double x) { return wxIsSameDouble(x, 0.); }
 
-    #if defined(HAVE_ROUND) && !defined(HAVE_DECL_ROUND)
-        extern "C" double round(double);
-    #endif
     inline int wxRound(double x)
     {
         #if defined(HAVE_ROUND)