diff --git a/libs/ardour/io.cc b/libs/ardour/io.cc
index 98484c22de..b8747a5907 100644
--- a/libs/ardour/io.cc
+++ b/libs/ardour/io.cc
@@ -18,11 +18,12 @@
 
 #include <fstream>
 #include <algorithm>
+#include <cmath>
+
 #include <unistd.h>
 #include <locale.h>
 #include <errno.h>
 
-
 #include <glibmm.h>
 #include <glibmm/thread.h>
 
@@ -47,18 +48,6 @@
 
 #include "i18n.h"
 
-#include <cmath>
-
-/*
-  A bug in OS X's cmath that causes isnan() and isinf() to be
-  "undeclared". the following works around that
-*/
-
-#if defined(__APPLE__) && defined(__MACH__)
-extern "C" int isnan (double);
-extern "C" int isinf (double);
-#endif
-
 #define BLOCK_PROCESS_CALLBACK() Glib::Mutex::Lock em (AudioEngine::instance()->process_lock())
 
 using namespace std;