diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index b1db3844..83f5df2b 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -11,7 +11,7 @@ env:
 
 jobs:
   shellcheck:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-24.04
     steps:
     - uses: actions/checkout@v4
     - name: shellcheck
@@ -19,7 +19,7 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [ubuntu-22.04, macos-12]
+        os: [ubuntu-24.04, macos-13, macos-14]
         fortran: [fortran-off, fortran-on]
         shared: [shared-off, shared-on]
 
@@ -41,12 +41,12 @@ jobs:
                 -DCMAKE_INSTALL_PREFIX=$HOME/mpitrampoline
             ;;
         macOS)
-            # Use GCC-12 from Homebrew
+            # Use GCC-14 from Homebrew
             cmake -B ${{github.workspace}}/build \
                 -DENABLE_FORTRAN=${fortran} \
-                -DCMAKE_C_COMPILER=gcc-12 \
-                -DCMAKE_CXX_COMPILER=g++-12 \
-                -DCMAKE_Fortran_COMPILER=gfortran-12 \
+                -DCMAKE_C_COMPILER=gcc-14 \
+                -DCMAKE_CXX_COMPILER=g++-14 \
+                -DCMAKE_Fortran_COMPILER=gfortran-14 \
                 -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} \
                 -DBUILD_SHARED_LIBS=${shared} \
                 -DCMAKE_INSTALL_PREFIX=$HOME/mpitrampoline
diff --git a/CITATION.cff b/CITATION.cff
index 8e2f3f77..9a17b2a2 100644
--- a/CITATION.cff
+++ b/CITATION.cff
@@ -5,6 +5,6 @@ authors:
     given-names: Erik
     orcid: https://orcid.org/0000-0002-4518-9017
 title: MPItrampoline
-version: v5.4.0
+version: v5.4.1
 doi: 10.5281/zenodo.6174408
-date-released: 2023-06-16
+date-released: 2024-08-29
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9369d6e2..84eccc5c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.12...3.20)
 project(
-  MPItrampoline VERSION 5.4.0
+  MPItrampoline VERSION 5.4.1
   DESCRIPTION "MPI trampoline"
   HOMEPAGE_URL "https://github.com/eschnett/MPItrampoline"
   LANGUAGES NONE
diff --git a/src/mpi.c b/src/mpi.c
index ef3e9dc7..031a536c 100644
--- a/src/mpi.c
+++ b/src/mpi.c
@@ -230,21 +230,21 @@ int PMPI_Pcontrol(int level, ...) { return MPI_SUCCESS; }
 
 // Sentinel values
 
-char **mpiabi_argv_null_ptr_;
-char ***mpiabi_argvs_null_ptr_;
+char **mpiabi_argv_null_ptr_ __attribute__((__aligned__(64))) = 0;
+char ***mpiabi_argvs_null_ptr_ __attribute__((__aligned__(64))) = 0;
 
-MPI_Fint *mpiabi_bottom_ptr_;
+MPI_Fint *mpiabi_bottom_ptr_ __attribute__((__aligned__(64))) = 0;
 
-MPI_Fint *mpiabi_errcodes_ignore_ptr_;
+MPI_Fint *mpiabi_errcodes_ignore_ptr_ __attribute__((__aligned__(64))) = 0;
 
-MPI_Fint *mpiabi_in_place_ptr_;
+MPI_Fint *mpiabi_in_place_ptr_ __attribute__((__aligned__(64))) = 0;
 
-MPI_Fint *mpiabi_status_ignore_ptr_;
-MPI_Fint *mpiabi_statuses_ignore_ptr_;
+MPI_Fint *mpiabi_status_ignore_ptr_ __attribute__((__aligned__(64))) = 0;
+MPI_Fint *mpiabi_statuses_ignore_ptr_ __attribute__((__aligned__(64))) = 0;
 
-MPI_Fint *mpiabi_unweighted_ptr_;
+MPI_Fint *mpiabi_unweighted_ptr_ __attribute__((__aligned__(64))) = 0;
 
-MPI_Fint *mpiabi_weights_empty_ptr_;
+MPI_Fint *mpiabi_weights_empty_ptr_ __attribute__((__aligned__(64))) = 0;
 
 #include "mpi_defn_constants_fortran.h"
 #include "mpi_defn_functions_fortran.h"