diff --git a/hak/matrix-seshat/build.ts b/hak/matrix-seshat/build.ts
index a2a8bbb4..2dbde84b 100644
--- a/hak/matrix-seshat/build.ts
+++ b/hak/matrix-seshat/build.ts
@@ -19,31 +19,14 @@ import childProcess from "child_process";
 import HakEnv from "../../scripts/hak/hakEnv";
 import { DependencyInfo } from "../../scripts/hak/dep";
 
-export default async function (hakEnv: HakEnv, moduleInfo: DependencyInfo): Promise<void> {
-    const env = hakEnv.makeGypEnv();
-
-    if (!hakEnv.isHost()) {
-        env.CARGO_BUILD_TARGET = hakEnv.getTargetId();
-    }
-
-    console.log("Running yarn install");
-    await new Promise<void>((resolve, reject) => {
-        const proc = childProcess.spawn("yarn" + (hakEnv.isWin() ? ".cmd" : ""), ["install"], {
-            cwd: moduleInfo.moduleBuildDir,
-            env,
-            shell: true,
-            stdio: "inherit",
-        });
-        proc.on("exit", (code) => {
-            code ? reject(code) : resolve();
-        });
-    });
-
-    const buildTarget = hakEnv.wantsStaticSqlCipher() ? "build-bundled" : "build";
-
-    console.log("Running yarn build");
-    await new Promise<void>((resolve, reject) => {
-        const proc = childProcess.spawn("yarn" + (hakEnv.isWin() ? ".cmd" : ""), ["run", buildTarget], {
+function run(
+    moduleInfo: DependencyInfo,
+    cmd: string,
+    args: string[],
+    env: Record<string, string | undefined>,
+): Promise<void> {
+    return new Promise<void>((resolve, reject) => {
+        const proc = childProcess.spawn(cmd, args, {
             cwd: moduleInfo.moduleBuildDir,
             env,
             shell: true,
@@ -54,3 +37,20 @@ export default async function (hakEnv: HakEnv, moduleInfo: DependencyInfo): Prom
         });
     });
 }
+
+export default async function (hakEnv: HakEnv, moduleInfo: DependencyInfo): Promise<void> {
+    const env = hakEnv.makeGypEnv();
+
+    if (!hakEnv.isHost()) {
+        env.CARGO_BUILD_TARGET = hakEnv.getTargetId();
+    }
+    const yarnCmd = "yarn" + (hakEnv.isWin() ? ".cmd" : "");
+
+    console.log("Running yarn install");
+    await run(moduleInfo, yarnCmd, ["install"], env);
+
+    const buildTarget = hakEnv.wantsStaticSqlCipher() ? "build-bundled" : "build";
+
+    console.log("Running yarn build");
+    await run(moduleInfo, yarnCmd, ["run", buildTarget], env);
+}