diff --git a/public/src/client/chats.js b/public/src/client/chats.js
index e21181cdc0..39cf3519c5 100644
--- a/public/src/client/chats.js
+++ b/public/src/client/chats.js
@@ -200,7 +200,7 @@ define('forum/chats', [
 		textarea.on('input', function () {
 			const isAtBottom = messages.isAtBottom(parent.find('.chat-content'));
 			textarea.css({ height: 0 });
-			textarea.css({ height: textarea.prop('scrollHeight') + 'px' });
+			textarea.css({ height: messages.calcAutoTextAreaHeight(textarea) + 'px' });
 			if (isAtBottom) {
 				messages.scrollToBottom(parent.find('.chat-content'));
 			}
diff --git a/public/src/client/chats/messages.js b/public/src/client/chats/messages.js
index 6f5dd27a28..ce6f6cb18f 100644
--- a/public/src/client/chats/messages.js
+++ b/public/src/client/chats/messages.js
@@ -54,16 +54,21 @@ define('forum/chats/messages', [
 
 	messages.updateTextAreaHeight = function (chatContentEl) {
 		const textarea = chatContentEl.find('[component="chat/input"]');
+		textarea.css({ height: messages.calcAutoTextAreaHeight(textarea) + 'px' });
+	};
+
+	messages.calcAutoTextAreaHeight = function (textarea) {
 		const scrollHeight = textarea.prop('scrollHeight');
-		textarea.css({ height: scrollHeight + 'px' });
+		const borderTopWidth = parseFloat(textarea.css('border-top-width'), 10) || 0;
+		const borderBottomWidth = parseFloat(textarea.css('border-bottom-width'), 10) || 0;
+		return scrollHeight + borderTopWidth + borderBottomWidth;
 	};
 
 	function autoresizeTextArea(textarea) {
-		const scrollHeight = textarea.prop('scrollHeight');
-		textarea.css({ height: scrollHeight + 'px' });
+		textarea.css({ height: messages.calcAutoTextAreaHeight(textarea) + 'px' });
 		textarea.on('input', function () {
 			textarea.css({ height: 0 });
-			textarea.css({ height: textarea.prop('scrollHeight') + 'px' });
+			textarea.css({ height: messages.calcAutoTextAreaHeight(textarea) + 'px' });
 		});
 	}