diff --git a/pkgs/by-name/op/openmolcas/nevpt2.patch b/pkgs/by-name/op/openmolcas/nevpt2.patch
index a2ad9071c120..c2af9edcbdee 100644
--- a/pkgs/by-name/op/openmolcas/nevpt2.patch
+++ b/pkgs/by-name/op/openmolcas/nevpt2.patch
@@ -1,24 +1,3 @@
---- a/src/gctime.c
-+++ b/src/gctime.c
-@@ -1,14 +1,15 @@
-+#include <string.h>
- typedef long f77_int;     /* Fortran integer type */
- typedef char * f77_char;    /* Fortran character argument */
- #define CH_F2C(X) ((char *) (X))  /* How to get char ptr from F77 argument */
--gctime (fstr, lstr) f77_char *fstr; int lstr; {
-+int gctime (fstr, lstr) f77_char *fstr; int lstr; {
-    long time(), t;
-    char *ctime();
-    t = time ( (long *) 0);
-    strcpy(CH_F2C(fstr),ctime(&t));
-    return (0);
-    }
--gctime_(fstr, lstr) f77_char *fstr; int lstr; {
-+int gctime_(fstr, lstr) f77_char *fstr; int lstr; {
-    long time(), t;
-    char *ctime();
-    t = time ( (long *) 0);
-
 --- a/CMakeLists.txt
 +++ b/CMakeLists.txt
 @@ -1,4 +1,4 @@
diff --git a/pkgs/by-name/op/openmolcas/package.nix b/pkgs/by-name/op/openmolcas/package.nix
index 0c3bde714e77..d542e8263c30 100644
--- a/pkgs/by-name/op/openmolcas/package.nix
+++ b/pkgs/by-name/op/openmolcas/package.nix
@@ -54,8 +54,8 @@ let
     src = fetchFromGitHub {
       owner = "qcscine";
       repo = "nevpt2";
-      rev = "e1484fd4901ae93ab0188bde417cf5dc440a8a3b"; # Must match tag in cmake/custom/nevpt2.cmake
-      hash = "sha256-Vl+FhwhJBbD/7U2CwsYE9BClSQYLJ8DKXV9EXxQUmz0=";
+      rev = "65a36d7db403d3b97089106a3ccc15344bf6bc86"; # Must match tag in cmake/custom/nevpt2.cmake
+      hash = "sha256-Ah2CjzW80KtRJoFPGYIKcY/vbn4IEWGFdf1TctQ4wD0=";
     };
     patches = [ ./nevpt2.patch ];
     installPhase = ''
@@ -67,13 +67,13 @@ let
 in
 stdenv.mkDerivation (finalAttrs: {
   pname = "openmolcas";
-  version = "26.06";
+  version = "26.10";
 
   src = fetchFromGitLab {
     owner = "Molcas";
     repo = "OpenMolcas";
     rev = "v${finalAttrs.version}";
-    hash = "sha256-y4eUfp8PIeWSuF4j9wT6C8z8rYFySUrNMa4ezI3/kXg=";
+    hash = "sha256-C67E4IrhVOkky1VsnbXykLKQDjToFpge587B0YJFV2c=";
   };
 
   patches = [
@@ -83,7 +83,7 @@ stdenv.mkDerivation (finalAttrs: {
 
   postPatch = ''
     # Using env fails in the sandbox
-    substituteInPlace Tools/pymolcas/export.py --replace \
+    substituteInPlace Tools/pymolcas/export.py --replace-fail \
       "/usr/bin/env','python3" "python3"
 
     # Pointing CMake to local QCMaquis and NEVPT2 archives