diff --git a/tools/sheet/index.ts b/tools/sheet/index.ts
index 90c4d0b9..d153cb8a 100644
--- a/tools/sheet/index.ts
+++ b/tools/sheet/index.ts
@@ -24,20 +24,28 @@ for (let i = 0; i < sheet.entries.length; i++) {
     }
 }
 
-// Store list of sprite files in a temp file, Windows can't handle large cli arg
-// lists. Just append a random string to the dest file
-const tmpFile = `${dest}.tmp.${crypto.randomBytes(6).readUIntLE(0,6).toString(36)}`;
-fs.writeFileSync(tmpFile, sheet.entries.join("\n"), 'utf8');
-
-cp.execFileSync("magick", [
+// Write list of filenames to stdin, Windows can't handle large cli arg lists.
+// Before we wrote a tmp file and deleted it afterwards, but apparently tup
+// can't track unlinkSync on Windows?
+const proc = cp.spawn("magick", [
     "montage",
-    `@${tmpFile}`,
+    "@-",
     "-background", "transparent",
     "-geometry", `${sheet.width}x${sheet.height}>`,
     "-gravity", "center",
     "-tile", `${sheet.tile}x`,
     "-depth", "8",
     dest
-]);
+], {
+    stdio: ['pipe', 'inherit', 'inherit']
+});
 
-fs.unlinkSync(tmpFile);
+// Write one at a time to avoid "malloc(): corrupted top size" error
+for (const entry of sheet.entries) {
+    proc.stdin.write(entry + "\n");
+}
+proc.stdin.end();
+
+proc.on('close', (code) => {
+    process.exit(code);
+});