diff --git a/.github/workflows/nightly-build.yml b/.github/workflows/nightly-build.yml
index b450c3c6..945ce76d 100644
--- a/.github/workflows/nightly-build.yml
+++ b/.github/workflows/nightly-build.yml
@@ -8,13 +8,13 @@ jobs:
     strategy:
       matrix:
         runner:
-          - RUNNER_OS: 'ubuntu-latest'
-            OS: linux-64
-            OS_NAME: linux_64
-            MINICONDA_INSTALLER_URL: https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh
-            C_COMPILER: gcc_linux-64 
-            FORTRAN_COMPILER: gfortran_linux-64
-            PROJECT_DIR: workdir/linux
+          - RUNNER_OS: 'macos-14'
+            OS: osx-arm64
+            OS_NAME: osx_arm64
+            MINICONDA_INSTALLER_URL: https://repo.anaconda.com/miniconda/Miniconda3-latest-MacOSX-arm64.sh
+            C_COMPILER: clang_osx-arm64 
+            FORTRAN_COMPILER: gfortran_osx-arm64
+            PROJECT_DIR: workdir/macos_arm64
         python_version: ['3.10']
     runs-on: ${{ matrix.runner.RUNNER_OS }}
     env:
diff --git a/Test/test_singletons.c b/Test/test_singletons.c
index acb02d81..3b6e7996 100644
--- a/Test/test_singletons.c
+++ b/Test/test_singletons.c
@@ -86,6 +86,7 @@ static void run_test()
     double scalar;
     int nlon, nlat, nlev;
     int zfactor_id;
+    int i;
 
     int axes_ids[5];
     int zfactor_axis_ids[3];
@@ -138,15 +139,35 @@ static void run_test()
     if (cmor_zfactor(&zfactor_id, id_alev, (char *) "p0", (char *) "Pa", 0, 0, 
                 'd', (void *) p0, NULL) != 0)
         fail("cmor_zfactor(p0)");
+        printf("cmor_vars[%d].ndims = %d\n", zfactor_id, cmor_vars[zfactor_id].ndims);
+        for(i = 0; i < cmor_vars[zfactor_id].ndims; ++i){
+            printf("cmor_vars[%d].axes_ids[%d].axes_ids = %d\n", zfactor_id, i, cmor_vars[zfactor_id].axes_ids[i]);
+            printf("cmor_axes[%d].id = %s\n", cmor_vars[zfactor_id].axes_ids[i], cmor_axes[cmor_vars[zfactor_id].axes_ids[i]].id);
+        }
     if (cmor_zfactor(&zfactor_id, id_alev, (char *) "b", (char *) "", 1, &lev_id_array[0], 
                 'd', (void *) b_val, (void *) b_bnds) != 0)
         fail("cmor_zfactor(b)");
+        printf("cmor_vars[%d].ndims = %d\n", zfactor_id, cmor_vars[zfactor_id].ndims);
+        for(i = 0; i < cmor_vars[zfactor_id].ndims; ++i){
+            printf("cmor_vars[%d].axes_ids[%d].axes_ids = %d\n", zfactor_id, i, cmor_vars[zfactor_id].axes_ids[i]);
+            printf("cmor_axes[%d].id = %s\n", cmor_vars[zfactor_id].axes_ids[i], cmor_axes[cmor_vars[zfactor_id].axes_ids[i]].id);
+        }
     if (cmor_zfactor(&zfactor_id, id_alev, (char *) "a", (char *) "", 1, &lev_id_array[0], 
                 'd', (void *) a_val, (void *) a_bnds) != 0)
         fail("cmor_zfactor(a)");
+        printf("cmor_vars[%d].ndims = %d\n", zfactor_id, cmor_vars[zfactor_id].ndims);
+        for(i = 0; i < cmor_vars[zfactor_id].ndims; ++i){
+            printf("cmor_vars[%d].axes_ids[%d].axes_ids = %d\n", zfactor_id, i, cmor_vars[zfactor_id].axes_ids[i]);
+            printf("cmor_axes[%d].id = %s\n", cmor_vars[zfactor_id].axes_ids[i], cmor_axes[cmor_vars[zfactor_id].axes_ids[i]].id);
+        }
     if (cmor_zfactor(&zfactor_id, id_alev, (char *) "ps1", (char *) "Pa", 3, zfactor_axis_ids, 
                 'd', NULL, NULL) != 0)
         fail("cmor_zfactor(ps1)");
+        printf("cmor_vars[%d].ndims = %d\n", zfactor_id, cmor_vars[zfactor_id].ndims);
+        for(i = 0; i < cmor_vars[zfactor_id].ndims; ++i){
+            printf("cmor_vars[%d].axes_ids[%d].axes_ids = %d\n", zfactor_id, i, cmor_vars[zfactor_id].axes_ids[i]);
+            printf("cmor_axes[%d].id = %s\n", cmor_vars[zfactor_id].axes_ids[i], cmor_axes[cmor_vars[zfactor_id].axes_ids[i]].id);
+        }
 
     /*
      * No singleton dimensions are passed.