$NetBSD: patch-ab,v 1.1.1.1 2010/08/27 11:43:05 adam Exp $

--- src/analysis/interpolation/qgsinterpolator.cpp.orig	2009-12-14 12:39:35.000000000 +0000
+++ src/analysis/interpolation/qgsinterpolator.cpp
@@ -92,7 +92,7 @@ int QgsInterpolator::cacheBaseData()
           continue;
         }
         attributeValue = att_it.value().toDouble( &attributeConversionOk );
-        if ( !attributeConversionOk || isnan( attributeValue ) ) //don't consider vertices with attributes like 'nan' for the interpolation
+        if ( !attributeConversionOk || isnanf( attributeValue ) ) //don't consider vertices with attributes like 'nan' for the interpolation
         {
           continue;
         }
