diff --git a/src/loader.ts b/src/loader.ts
index e351e2220..1d5740b7a 100644
--- a/src/loader.ts
+++ b/src/loader.ts
@@ -213,7 +213,7 @@ export class LoaderResolver {
       const eext = fext.slice(0, -iext.length); // .zip
       const loader = new CommandLoader({
         command: command ?? commandPath,
-        args: params ? args.concat(defineParams(params)) : args,
+        args: withParams(args, params),
         path,
         params,
         root: this.root,
@@ -332,6 +332,10 @@ export class LoaderResolver {
   }
 }
 
+export function withParams(args: string[], params?: Params): string[] {
+  return params ? args.concat(defineParams(params)) : args;
+}
+
 function defineParams(params: Params): string[] {
   return Object.entries(params)
     .filter(([name]) => /^[a-z0-9_]+$/i.test(name)) // ignore non-ASCII parameters
diff --git a/src/markdown.ts b/src/markdown.ts
index a9d2e6d6e..52834aa1a 100644
--- a/src/markdown.ts
+++ b/src/markdown.ts
@@ -18,6 +18,7 @@ import {parseInfo} from "./info.js";
 import {transformJavaScriptSync} from "./javascript/module.js";
 import type {JavaScriptNode} from "./javascript/parse.js";
 import {parseJavaScript} from "./javascript/parse.js";
+import {withParams} from "./loader.js";
 import {isAssetPath, relativePath} from "./path.js";
 import {parsePlaceholder} from "./placeholder.js";
 import type {Params} from "./route.js";
@@ -282,10 +283,19 @@ export async function parseMarkdown(input: string, options: ParseOptions): Promi
       const root: Comment = roots.get(fragment.id);
       const [command, ...args] = interpreters.get(`.${fragment.tag}`)!;
       let target = "";
-      const subprocess = spawn(command, args, {
-        windowsHide: true,
-        stdio: ["pipe", "pipe", "inherit"]
-      });
+      const subprocess = spawn(
+        command,
+        withParams(
+          command === "sh"
+            ? args.concat("-s", "--") // TODO make this configurable
+            : args.concat("-"), // TODO make this configurable
+          params
+        ),
+        {
+          windowsHide: true,
+          stdio: ["pipe", "pipe", "inherit"]
+        }
+      );
       subprocess.stdin.write(fragment.source);
       subprocess.stdin.end();
       subprocess.stdout.on("data", (data) => {