diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 80eaccb..ec4ea52 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -104,6 +104,59 @@ jobs:
       - name: Run tests
         run: cd coreutils && make test
 
+  # There is no Vinix runner on GitHub, so this job does not run the suite. It
+  # cross-compiles every tool for the target instead, which is the check that
+  # catches what the platform-gated files in src/*/ get wrong: a tool whose
+  # shared .v and its _nix/_default variants disagree will not build for Vinix
+  # even though it builds for Windows, and that is exactly how `timeout` was
+  # broken on all three Unix targets before this existed.
+  vinix-cross-build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Latest V
+        uses: actions/checkout@v6
+        with:
+          repository: vlang/v
+          path: v
+      - name: Build V
+        run: cd v && make && sudo ./v symlink && cd -
+      - name: Checkout Coreutils
+        uses: actions/checkout@v6
+        with:
+          path: coreutils
+      - name: V doctor
+        run: v doctor
+      - name: Cross-compile every tool for Vinix
+        shell: bash
+        run: |
+          cd coreutils
+          # Read the ignore list straight out of build.vsh so the two cannot
+          # drift. `grep -n` and `sed -n` are both 1-based, so the key's own
+          # line is the one to read and there is no offset to get wrong.
+          # The key word itself is dropped, since it is not a tool name.
+          ignored=$(grep -E "^\s*'vinix':" build.vsh | grep -oE "'[a-z0-9_]+'" | tr -d "'"
+            | grep -vx 'vinix')
+          echo "vinix ignores: ${ignored:-<none>}"
+          ok=0 skipped=0 failed=0
+          for d in src/*/; do
+            name=$(basename "$d")
+            # A tool directory is one holding at least one .v file.
+            compgen -G "$d*.v" >/dev/null || continue
+            if printf '%s\n' "$ignored" | grep -qx "$name"; then
+              skipped=$((skipped + 1))
+              continue
+            fi
+            if v -os vinix -o "/tmp/vinix_${name}.c" "$d" >/dev/null 2>&1; then
+              ok=$((ok + 1))
+            else
+              echo "::error file=$d::cross-compile for vinix failed: $name"
+              v -os vinix -o "/tmp/vinix_${name}.c" "$d" 2>&1 | head -20 || true
+              failed=$((failed + 1))
+            fi
+          done
+          echo "vinix cross-compile: ok=$ok skipped=$skipped failed=$failed"
+          [ "$failed" -eq 0 ]
+
   ubuntu-gnu-coreutils:
     runs-on: ubuntu-latest
     steps:
diff --git a/build.vsh b/build.vsh
index 9308ea4..6d3291d 100755
--- a/build.vsh
+++ b/build.vsh
@@ -43,7 +43,14 @@ const ignore_dirs = {
 		// TODO: nohup is included in Win32 version
 		'nohup',
 	]
+	// Vinix is a Unix-like, so it shares the macOS list. The two categories
+	// differ for a reason worth spelling out: `stat` and `sync` are excluded on
+	// macOS because the BSD syscall surface differs from Linux, and Vinix
+	// follows POSIX closely enough that they do build there; `uptime` is
+	// excluded everywhere because it reads the utmp database, which Vinix
+	// does not implement yet.
 	'macos':   ['stat', 'sync', 'uptime']
+	'vinix':   ['uptime']
 }[user_os()] or { [] }
 
 unbuffer_stdout()
diff --git a/src/timeout/timeout.v b/src/timeout/timeout.v
index 943685d..3f75cdf 100644
--- a/src/timeout/timeout.v
+++ b/src/timeout/timeout.v
@@ -249,7 +249,7 @@ fn handle_timeout(mut p os.Process, kill_after_ms i64, signal string, preserve_s
 	if verbose {
 		eprintln('${app_name}: sending signal ${signal} to command')
 	}
-	terminate_process(p, sig_num, !foreground)
+	terminate_process(mut &p, sig_num, !foreground)
 
 	if kill_after_ms > 0 {
 		kill_start := time.now()
@@ -263,7 +263,7 @@ fn handle_timeout(mut p os.Process, kill_after_ms i64, signal string, preserve_s
 					if verbose {
 						eprintln('${app_name}: sending signal KILL to command')
 					}
-					terminate_process(p, 9, !foreground)
+					terminate_process(mut &p, 9, !foreground)
 				}
 				return handle_process_exit(mut p, preserve_status, 124)
 			}
diff --git a/src/timeout/timeout_default.c.v b/src/timeout/timeout_default.c.v
index 48f756b..a912be6 100644
--- a/src/timeout/timeout_default.c.v
+++ b/src/timeout/timeout_default.c.v
@@ -4,7 +4,7 @@ fn setup_process_group(p os.Process, foreground bool) {
 	// Fallback
 }
 
-fn terminate_process(p os.Process, sig_num int, process_group bool) {
+fn terminate_process(mut p &os.Process, sig_num int, process_group bool) {
 	// Fallback: try to kill the process
 	p.signal_kill()
 }
diff --git a/src/timeout/timeout_nix.c.v b/src/timeout/timeout_nix.c.v
index 00f4349..5a2d001 100644
--- a/src/timeout/timeout_nix.c.v
+++ b/src/timeout/timeout_nix.c.v
@@ -12,7 +12,7 @@ fn setup_process_group(p os.Process, foreground bool) {
 	}
 }
 
-fn terminate_process(p os.Process, sig_num int, process_group bool) {
+fn terminate_process(mut p &os.Process, sig_num int, process_group bool) {
 	pid := if process_group { -p.pid } else { p.pid }
 	C.kill(pid, sig_num)
 }
diff --git a/src/timeout/timeout_windows.c.v b/src/timeout/timeout_windows.c.v
index c0c688a..a035f98 100644
--- a/src/timeout/timeout_windows.c.v
+++ b/src/timeout/timeout_windows.c.v
@@ -7,7 +7,7 @@ fn setup_process_group(p os.Process, foreground bool) {
 // A pointer, because signalling a process changes it. Passing it by value, as the
 // nix version can, made the compiler reference it for us and then reject that as
 // deprecated automatic referencing.
-fn terminate_process(p os.Process, sig_num int, process_group bool) {
+fn terminate_process(mut p &os.Process, sig_num int, process_group bool) {
 	// TERM, Windows doesn't seem to support signals like Unixes does
 	if sig_num == 15 {
 		p.signal_term()