diff --git a/scripts/dev.js b/scripts/dev.js
index 80e505d8..10d6ac36 100644
--- a/scripts/dev.js
+++ b/scripts/dev.js
@@ -13,7 +13,7 @@ args.push("--dev");
 args.push("--secret");
 args.push(secret);
 
-let buildproc, runproc, timeout;
+let buildproc, runproc;
 function run(changedFile) {
     if (changedFile) {
         console.log(`Change to ${changedFile} detected`);
@@ -28,19 +28,20 @@ function run(changedFile) {
         runproc = undefined;
     }
 
-    clearTimeout(timeout);
-    timeout = setTimeout(function () {
-        buildproc = spawn("npm", ["run", "build:dev"], { stdio: "inherit", shell: true });
-        buildproc.on("exit", code => {
-            buildproc = undefined;
-            if (code === 0) {
-                runproc = spawn("npm", ["run", "start", "--", ...args], { stdio: "inherit", shell: true });
-                runproc.on("exit", () => {
-                    runproc = undefined;
-                });
-            }
-        });
-    }, 20);
+    const thisbuildproc = spawn("npm", ["run", "build:dev"], { stdio: "inherit", shell: true });
+    buildproc = thisbuildproc;
+    buildproc.on("exit", code => {
+        if (buildproc !== thisbuildproc) {
+            return;
+        }
+        buildproc = undefined;
+        if (code === 0) {
+            runproc = spawn("npm", ["run", "start", "--", ...args], { stdio: "inherit", shell: true });
+            runproc.on("exit", () => {
+                runproc = undefined;
+            });
+        }
+    });
 }
 
 run();