diff --git a/.github/workflows/optional.yml b/.github/workflows/optional.yml
new file mode 100644
index 0000000000..d2002bd674
--- /dev/null
+++ b/.github/workflows/optional.yml
@@ -0,0 +1,47 @@
+name: optional
+on:
+  pull_request:
+    types: [labeled, opened, synchronize, reopened]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event_name == 'pull_request' && github.head_ref || github.sha }}
+  cancel-in-progress: true
+
+env:
+  INSTALL_PREFIX: ${{ github.workspace }}/nvim-install
+  # Double test timeout since it's running via qemu
+  TEST_TIMEOUT: 2400
+  # TEST_FILE: test/functional/shada
+  # TEST_FILTER: foo
+
+jobs:
+  s390x:
+    if: contains(github.event.pull_request.labels.*.name, 'ci-s390x')
+    strategy:
+      fail-fast: false
+      matrix:
+        test: [functionaltest, oldtest]
+    runs-on: ubuntu-latest
+    timeout-minutes: 60
+    steps:
+      - run: docker run --rm --privileged multiarch/qemu-user-static:register --reset
+      - uses: docker://multiarch/ubuntu-core:s390x-focal
+        with:
+          # Docker runs the command as root, but we want the build/test to run
+          # as non-root so permissions based tests run correctly
+          args: >
+            bash -c
+            "
+            apt-get -y update &&
+            DEBIAN_FRONTEND=noninteractive apt-get -y install build-essential cmake curl gettext ninja-build unzip locales-all cpanminus git attr libattr1-dev  &&
+            useradd --create-home qemuci &&
+            chown -R qemuci. . &&
+            runuser -u qemuci -- git clone --depth=1 https://github.com/neovim/neovim.git &&
+            cd neovim &&
+            runuser -u qemuci -- git fetch origin ${{ github.ref }}:pr &&
+            runuser -u qemuci -- git switch pr &&
+            runuser -u qemuci -- cmake -S cmake.deps -B .deps -G Ninja -D USE_BUNDLED_LUAJIT=OFF -D USE_BUNDLED_LUA=ON &&
+            runuser -u qemuci -- cmake --build .deps &&
+            runuser -u qemuci -- cmake -B build -G Ninja -D PREFER_LUA=ON &&
+            runuser -u qemuci -- make ${{ matrix.test }}
+            "
diff --git a/src/nvim/api/extmark.c b/src/nvim/api/extmark.c
index eb49587d03..1b4d805d87 100644
--- a/src/nvim/api/extmark.c
+++ b/src/nvim/api/extmark.c
@@ -222,7 +222,9 @@ static Array extmark_to_array(const ExtmarkInfo *extmark, bool id, bool add_dict
     }
 
     if (decor->conceal) {
-      String name = cstr_to_string((char *)&decor->conceal_char);
+      char bytes[MB_MAXCHAR + 1] = {0};
+      utf_char2bytes(decor->conceal_char, bytes);
+      String name = cstr_to_string(bytes);
       PUT(dict, "conceal", STRING_OBJ(name));
     }
 
diff --git a/src/nvim/eval/vars.c b/src/nvim/eval/vars.c
index 9120cc4471..09a5560d2b 100644
--- a/src/nvim/eval/vars.c
+++ b/src/nvim/eval/vars.c
@@ -1644,7 +1644,7 @@ static void set_option_from_tv(const char *varname, typval_T *varp)
       emsg(_(e_stringreq));
       return;
     }
-    numval = (long)varp->vval.v_number;
+    numval = varp->vval.v_bool;
     strval = "0";  // avoid using "false"
   } else {
     numval = (long)tv_get_number_chk(varp, &error);
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 4658ca4a3a..44a4ec2843 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -2248,7 +2248,7 @@ static const char *set_bool_option(const int opt_idx, char *const varp, const in
 
   if (options[opt_idx].flags & P_UI_OPTION) {
     ui_call_option_set(cstr_as_string(options[opt_idx].fullname),
-                       BOOLEAN_OBJ(*varp));
+                       BOOLEAN_OBJ(*(int *)varp));
   }
   if ((int *)varp == &p_ru || (int *)varp == &p_sc) {
     // in case 'ruler' or 'showcmd' changed