diff --git a/index.js b/index.js
index f8297f5..4727186 100644
--- a/index.js
+++ b/index.js
@@ -120,8 +120,38 @@ export default function normalizeUrl(urlString, options) {
 	}
 
 	// Remove duplicate slashes if not preceded by a protocol
+	// NOTE: This could be implemented using a single negative lookbehind
+	// regex, but we avoid that to maintain compatibility with older js engines
+	// which do not have support for that feature.
 	if (urlObject.pathname) {
-		urlObject.pathname = urlObject.pathname.replace(/(?<!\b[a-z][a-z\d+\-.]{1,50}:)\/{2,}/g, '/');
+		// TODO: Replace everything below with `urlObject.pathname = urlObject.pathname.replace(/(?<!\b[a-z][a-z\d+\-.]{1,50}:)\/{2,}/g, '/');` when Safari supports negative lookbehind.
+
+		// Split the string by occurrences of this protocol regex, and perform
+		// duplicate-slash replacement on the strings between those occurrences
+		// (if any).
+		const protocolRegex = /\b[a-z][a-z\d+\-.]{1,50}:\/\//g;
+
+		let lastIndex = 0;
+		let result = '';
+		for (;;) {
+			const match = protocolRegex.exec(urlObject.pathname);
+			if (!match) {
+				break;
+			}
+
+			const protocol = match[0];
+			const protocolAtIndex = match.index;
+			const intermediate = urlObject.pathname.slice(lastIndex, protocolAtIndex);
+
+			result += intermediate.replace(/\/{2,}/g, '/');
+			result += protocol;
+			lastIndex = protocolAtIndex + protocol.length;
+		}
+
+		const remnant = urlObject.pathname.slice(lastIndex, urlObject.pathname.length);
+		result += remnant.replace(/\/{2,}/g, '/');
+
+		urlObject.pathname = result;
 	}
 
 	// Decode URI octets
diff --git a/package.json b/package.json
index 9d77c57..ee54c3b 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "normalize-url",
-	"version": "7.0.0",
+	"version": "7.0.1",
 	"description": "Normalize a URL",
 	"license": "MIT",
 	"repository": "sindresorhus/normalize-url",
@@ -16,7 +16,7 @@
 		"node": ">=12.20"
 	},
 	"scripts": {
-		"test": "xo && nyc ava && tsd"
+		"test": "xo && c8 ava && tsd"
 	},
 	"files": [
 		"index.js",
@@ -39,11 +39,12 @@
 	],
 	"devDependencies": {
 		"ava": "^3.15.0",
-		"nyc": "^15.1.0",
+		"c8": "^7.7.3",
 		"tsd": "^0.17.0",
+		"typescript": "^4.3.5",
 		"xo": "^0.41.0"
 	},
-	"nyc": {
+	"c8": {
 		"reporter": [
 			"text",
 			"lcov"
diff --git a/test.js b/test.js
index d19b128..149b51a 100644
--- a/test.js
+++ b/test.js
@@ -269,19 +269,19 @@ test('invalid urls', t => {
 	t.throws(() => {
 		normalizeUrl('http://');
 	}, {
-		message: 'Invalid URL',
+		message: /^Invalid URL/,
 	});
 
 	t.throws(() => {
 		normalizeUrl('/');
 	}, {
-		message: 'Invalid URL',
+		message: /^Invalid URL/,
 	});
 
 	t.throws(() => {
 		normalizeUrl('/relative/path/');
 	}, {
-		message: 'Invalid URL',
+		message: /^Invalid URL/,
 	});
 });