diff --git a/addons/xterm-addon-search/src/SearchAddon.api.ts b/addons/xterm-addon-search/src/SearchAddon.api.ts
index 186cccca..14e12a8c 100644
--- a/addons/xterm-addon-search/src/SearchAddon.api.ts
+++ b/addons/xterm-addon-search/src/SearchAddon.api.ts
@@ -111,12 +111,7 @@ async function openTerminal(options: ITerminalOptions = {}): Promise<void> {
 }
 
 async function writeSync(data: string): Promise<void> {
-  await page.evaluate(`window.term.write('${data}');`);
-  while (true) {
-    if (await page.evaluate(`window.term._core._writeBuffer.length === 0`)) {
-      break;
-    }
-  }
+  return page.evaluate(`new Promise(resolve => window.term.write('${data}', resolve))`);
 }
 
 function makeData(length: number): string {
diff --git a/addons/xterm-addon-webgl/src/WebglRenderer.api.ts b/addons/xterm-addon-webgl/src/WebglRenderer.api.ts
index 82ac0adf..66be22d9 100644
--- a/addons/xterm-addon-webgl/src/WebglRenderer.api.ts
+++ b/addons/xterm-addon-webgl/src/WebglRenderer.api.ts
@@ -145,12 +145,7 @@ async function openTerminal(options: ITerminalOptions = {}): Promise<void> {
 }
 
 async function writeSync(data: string): Promise<void> {
-  await page.evaluate(`window.term.write('${data}');`);
-  while (true) {
-    if (await page.evaluate(`window.term._core._writeBuffer.length === 0`)) {
-      break;
-    }
-  }
+  return page.evaluate(`new Promise(resolve => window.term.write('${data}', resolve))`);
 }
 
 async function getCellColor(col: number, row: number): Promise<number[]> {