diff --git a/pkgs/development/libraries/science/math/petsc/default.nix b/pkgs/development/libraries/science/math/petsc/default.nix
index 492ad63f27b6..911f0a1cf898 100644
--- a/pkgs/development/libraries/science/math/petsc/default.nix
+++ b/pkgs/development/libraries/science/math/petsc/default.nix
@@ -2,11 +2,11 @@
 
 stdenv.mkDerivation rec {
   pname = "petsc";
-  version = "3.12.4";
+  version = "3.13.0";
 
   src = fetchurl {
     url = "http://ftp.mcs.anl.gov/pub/petsc/release-snapshots/petsc-${version}.tar.gz";
-    sha256 = "1hw4f12v2xwrs37gjh83dbixhg0yxandqx7s7k5vlfx91l9l3aan";
+    sha256 = "0943bydmsq3sjwj3rxhb8hx58b1fm8vymny731557fs10g5zfbyz";
   };
 
   nativeBuildInputs = [ blas gfortran.cc.lib liblapack python ];
@@ -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]"