diff --git a/src/compiler/compile/render_ssr/handlers/shared/get_attribute_value.ts b/src/compiler/compile/render_ssr/handlers/shared/get_attribute_value.ts
index 5c89a7a008..9efb086854 100644
--- a/src/compiler/compile/render_ssr/handlers/shared/get_attribute_value.ts
+++ b/src/compiler/compile/render_ssr/handlers/shared/get_attribute_value.ts
@@ -9,7 +9,7 @@ export function get_class_attribute_value(attribute: Attribute): ESTreeExpressio
 	// handle special case — `class={possiblyUndefined}` with scoped CSS
 	if (attribute.chunks.length === 2 && (attribute.chunks[1] as Text).synthetic) {
 		const value = (attribute.chunks[0] as Expression).node;
-		return x`@escape(@null_to_empty(${value})) + "${(attribute.chunks[1] as Text).data}"`;
+		return x`@escape(@null_to_empty(${value}), 1) + "${(attribute.chunks[1] as Text).data}"`;
 	}
 
 	return get_attribute_value(attribute);
@@ -22,7 +22,7 @@ export function get_attribute_value(attribute: Attribute): ESTreeExpression {
 		.map((chunk) => {
 			return chunk.type === 'Text'
 				? string_literal(chunk.data.replace(/"/g, '"')) as ESTreeExpression
-				: x`@escape(${chunk.node})`;
+				: x`@escape(${chunk.node}, 1)`;
 		})
 		.reduce((lhs, rhs) => x`${lhs} + ${rhs}`);
 }
diff --git a/src/runtime/internal/ssr.ts b/src/runtime/internal/ssr.ts
index 2d843abb2f..022fb67ddb 100644
--- a/src/runtime/internal/ssr.ts
+++ b/src/runtime/internal/ssr.ts
@@ -32,16 +32,45 @@ export function spread(args, classes_to_add) {
 	return str;
 }
 
-export const escaped = {
-	'"': '"',
-	"'": ''',
-	'&': '&',
-	'<': '&lt;',
-	'>': '&gt;'
-};
+const ATTR_REGEX = /[&<"]/;
+const CONTENT_REGEX = /[&<]/;
+
+export function escape(html: string, attr: 0 | 1 = 0) {
+	if (typeof html !== 'string') return html;
+
+	const match = (attr ? ATTR_REGEX : CONTENT_REGEX).exec(html);
+	if (!match) return html;
+
+	let index = 0;
+	let lastIndex = 0;
+	let out = '';
+	let escape = '';
+
+	for (index = match.index; index < html.length; index++) {
+		switch (html.charCodeAt(index)) {
+			case 34: // "
+			if (!attr) continue;
+			escape = '&quot;';
+			break;
+			case 38: // &
+			escape = '&amp;';
+			break;
+			case 60: // <
+			escape = '&lt;';
+			break;
+			default:
+			continue;
+		}
+
+		if (lastIndex !== index) {
+			out += html.substring(lastIndex, index);
+		}
+
+		lastIndex = index + 1;
+		out += escape;
+	}
 
-export function escape(html) {
-	return String(html).replace(/["'&<>]/g, match => escaped[match]);
+	return lastIndex !== index ? out + html.substring(lastIndex, index) : out;
 }
 
 export function each(items, fn) {
@@ -129,7 +158,7 @@ export function create_ssr_component(fn) {
 
 export function add_attribute(name, value, boolean) {
 	if (value == null || (boolean && !value)) return '';
-	return ` ${name}${value === true ? '' : `=${typeof value === 'string' ? JSON.stringify(escape(value)) : `"${value}"`}`}`;
+	return ` ${name}${value === true ? '' : `=${typeof value === 'string' ? JSON.stringify(escape(value, 1)) : `"${value}"`}`}`;
 }
 
 export function add_classes(classes) {