Index: trunk/BNC/src/PPP_SSR_I/pppFilter.cpp
===================================================================
--- trunk/BNC/src/PPP_SSR_I/pppFilter.cpp	(revision 8252)
+++ trunk/BNC/src/PPP_SSR_I/pppFilter.cpp	(revision 8253)
@@ -295,7 +295,7 @@
   bancroft(BB, _xcBanc);
 
-  if (isnan(_xcBanc(1)) ||
-      isnan(_xcBanc(2)) ||
-      isnan(_xcBanc(3))) {
+  if (std::isnan(_xcBanc(1)) ||
+      std::isnan(_xcBanc(2)) ||
+      std::isnan(_xcBanc(3))) {
     return failure;
   }