diff --git a/pkgs/applications/science/chemistry/openmolcas/default.nix b/pkgs/applications/science/chemistry/openmolcas/default.nix
index 487558a23c19..d73e86d2f577 100644
--- a/pkgs/applications/science/chemistry/openmolcas/default.nix
+++ b/pkgs/applications/science/chemistry/openmolcas/default.nix
@@ -1,11 +1,11 @@
 { stdenv, fetchFromGitLab, cmake, gfortran, perl
 , openblas, hdf5-cpp, python3, texlive
 , armadillo, openmpi, globalarrays, openssh
-, makeWrapper
+, makeWrapper, fetchpatch
 } :
 
 let
-  version = "18.09";
+  version = "19.11";
   gitLabRev = "v${version}";
 
   python = python3.withPackages (ps : with ps; [ six pyparsing ]);
@@ -18,9 +18,19 @@ in stdenv.mkDerivation {
     owner = "Molcas";
     repo = "OpenMolcas";
     rev = gitLabRev;
-    sha256 = "1di1ygifx7ycfpwh25mv76xlv15wqfdmqzjsg5nani2d5z0arri2";
+    sha256 = "1wwqhkyyi7pw5x1ghnp83ir17zl5jsj7phhqxapybyi3bmg0i00q";
   };
 
+  patches = [ (fetchpatch {
+    name = "Fix-MPI-INT-size"; # upstream patch, fixes a Fortran compiler error
+    url = "https://gitlab.com/Molcas/OpenMolcas/commit/860e3350523f05ab18e49a428febac8a4297b6e4.patch";
+    sha256 = "0h96h5ikbi5l6ky41nkxmxfhjiykkiifq7vc2s3fdy1r1siv09sb";
+  }) (fetchpatch {
+    name = "fix-cisandbox"; # upstream patch, fixes a Fortran compiler error
+    url = "https://gitlab.com/Molcas/OpenMolcas/commit/d871590c8ce4689cd94cdbbc618954c65589393d.patch";
+    sha256 = "0dgz1w2rkglnis76spai3m51qa72j4bz6ppnk5zmzrr6ql7gwpgg";
+  })];
+
   nativeBuildInputs = [ perl cmake texlive.combined.scheme-minimal makeWrapper ];
   buildInputs = [
     gfortran