From eda71383301068896f23c510fb5b46c4c41ee148 Mon Sep 17 00:00:00 2001
From: yinonov <yinon.oved@vonage.com>
Date: Thu, 29 Dec 2022 09:51:11 +0200
Subject: [PATCH] =?UTF-8?q?add=20missing=20part=20attribute=20for=20tabpan?=
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# Pull Request

## 📖 Description

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### 🎫 Issues

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## 📑 Test Plan

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## ✅ Checklist

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## ⏭ Next Steps

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---
 packages/web-components/fast-foundation/src/tabs/tabs.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/web-components/fast-foundation/src/tabs/tabs.ts b/packages/web-components/fast-foundation/src/tabs/tabs.ts
index 2a7625ff44b..b0a3f3b93a3 100644
--- a/packages/web-components/fast-foundation/src/tabs/tabs.ts
+++ b/packages/web-components/fast-foundation/src/tabs/tabs.ts
@@ -345,7 +345,8 @@ export class Tabs extends FoundationElement {
         const prev: number = this.activeIndicatorRef[offsetProperty];
         this.activeIndicatorRef.style[gridProperty] = `${this.activeTabIndex + 1}`;
         const next: number = this.activeIndicatorRef[offsetProperty];
-        this.activeIndicatorRef.style[gridProperty] = `${this.prevActiveTabIndex + 1}`;
+        const gridPropertyValue = this.prevActiveTabIndex === -1 ? 0 : this.prevActiveTabIndex;
+        this.activeIndicatorRef.style[gridProperty] = `${gridPropertyValue + 1}`;
         const dif: number = next - prev;
         this.activeIndicatorRef.style.transform = `${translateProperty}(${dif}px)`;
         this.activeIndicatorRef.classList.add("activeIndicatorTransition");