diff --git a/pkgs/development/libraries/science/math/petsc/default.nix b/pkgs/development/libraries/science/math/petsc/default.nix
index 7b0b500d12d..911f0a1cf89 100644
--- a/pkgs/development/libraries/science/math/petsc/default.nix
+++ b/pkgs/development/libraries/science/math/petsc/default.nix
@@ -21,7 +21,7 @@ stdenv.mkDerivation rec {
     configureFlagsArray=(
       $configureFlagsArray
       "--CC=$CC"
-      "--with-cxx=g++"
+      "--with-cxx=$CXX"
       "--with-fc=0"
       "--with-mpi=0"
       "--with-blas-lib=[${blas}/lib/libblas.a,${gfortran.cc.lib}/lib/libgfortran.a]"