diff --git a/dune/solvers/solvers/cgsolver.cc b/dune/solvers/solvers/cgsolver.cc
index 82ea026023ed3c46b5fcef99eb08071cf4f000e4..7233e6095a963fc0ef24a3759f06f3d161ee27c1 100644
--- a/dune/solvers/solvers/cgsolver.cc
+++ b/dune/solvers/solvers/cgsolver.cc
@@ -134,7 +134,7 @@ void CGSolver<MatrixType, VectorType>::solve()
 
         normOfOldCorrection = normOfCorrection;
 
-        if (!isinf(convRate) && !isnan(convRate)) {
+        if (!std::isinf(convRate) && !std::isnan(convRate)) {
             totalConvRate *= convRate;
             this->maxTotalConvRate_ = std::max(this->maxTotalConvRate_, std::pow(totalConvRate, 1/((double)convRateCounter+1)));
             convRateCounter++;