diff --git a/path/_common/assert_path.ts b/path/_common/assert_path.ts
index abd021fd472a5..7033edcd1a79b 100644
--- a/path/_common/assert_path.ts
+++ b/path/_common/assert_path.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
 // Copyright the Browserify authors. MIT License.
 
-export function assertPath(path: string) {
+export function assertPath(path?: string) {
   if (typeof path !== "string") {
     throw new TypeError(
       `Path must be a string. Received ${JSON.stringify(path)}`,
diff --git a/path/_common/glob_to_reg_exp.ts b/path/_common/glob_to_reg_exp.ts
index 0a3dfbb4f7d54..155284d79a6b4 100644
--- a/path/_common/glob_to_reg_exp.ts
+++ b/path/_common/glob_to_reg_exp.ts
@@ -65,7 +65,7 @@ export function _globToRegExp(
 
   // Remove trailing separators.
   let newLength = glob.length;
-  for (; newLength > 1 && c.seps.includes(glob[newLength - 1]); newLength--);
+  for (; newLength > 1 && c.seps.includes(glob[newLength - 1]!); newLength--);
   glob = glob.slice(0, newLength);
 
   let regExpString = "";
@@ -80,11 +80,11 @@ export function _globToRegExp(
     let i = j;
 
     // Terminates with `i` at the non-inclusive end of the current segment.
-    for (; i < glob.length && !c.seps.includes(glob[i]); i++) {
+    for (; i < glob.length && !c.seps.includes(glob[i]!); i++) {
       if (inEscape) {
         inEscape = false;
         const escapeChars = inRange ? rangeEscapeChars : regExpEscapeChars;
-        segment += escapeChars.includes(glob[i]) ? `\\${glob[i]}` : glob[i];
+        segment += escapeChars.includes(glob[i]!) ? `\\${glob[i]}` : glob[i];
         continue;
       }
 
@@ -247,7 +247,7 @@ export function _globToRegExp(
         continue;
       }
 
-      segment += regExpEscapeChars.includes(glob[i]) ? `\\${glob[i]}` : glob[i];
+      segment += regExpEscapeChars.includes(glob[i]!) ? `\\${glob[i]}` : glob[i];
     }
 
     // Check for unclosed groups or a dangling backslash.
@@ -267,7 +267,7 @@ export function _globToRegExp(
     }
 
     // Terminates with `i` at the start of the next segment.
-    while (c.seps.includes(glob[i])) i++;
+    while (c.seps.includes(glob[i]!)) i++;
 
     // Check that the next value of `j` is indeed higher than the current value.
     if (!(i > j)) {
diff --git a/path/posix/join.ts b/path/posix/join.ts
index 0f7b152f60442..ad4bbae55d8e6 100644
--- a/path/posix/join.ts
+++ b/path/posix/join.ts
@@ -13,7 +13,7 @@ export function join(...paths: string[]): string {
 
   let joined: string | undefined;
   for (let i = 0, len = paths.length; i < len; ++i) {
-    const path = paths[i];
+    const path = paths[i]!;
     assertPath(path);
     if (path.length > 0) {
       if (!joined) joined = path;
diff --git a/path/posix/resolve.ts b/path/posix/resolve.ts
index 50022c0531ffd..196a08a568baf 100644
--- a/path/posix/resolve.ts
+++ b/path/posix/resolve.ts
@@ -16,7 +16,7 @@ export function resolve(...pathSegments: string[]): string {
   for (let i = pathSegments.length - 1; i >= -1 && !resolvedAbsolute; i--) {
     let path: string;
 
-    if (i >= 0) path = pathSegments[i];
+    if (i >= 0) path = pathSegments[i]!;
     else {
       // deno-lint-ignore no-explicit-any
       const { Deno } = globalThis as any;
diff --git a/path/windows/join.ts b/path/windows/join.ts
index 59f6777c50189..b17493dee81a3 100644
--- a/path/windows/join.ts
+++ b/path/windows/join.ts
@@ -16,7 +16,7 @@ export function join(...paths: string[]): string {
   let joined: string | undefined;
   let firstPart: string | null = null;
   for (let i = 0; i < paths.length; ++i) {
-    const path = paths[i];
+    const path = paths[i]!;
     assertPath(path);
     if (path.length > 0) {
       if (joined === undefined) joined = firstPart = path;
diff --git a/path/windows/resolve.ts b/path/windows/resolve.ts
index 1732ff6cb293a..c34f1e8c668fa 100644
--- a/path/windows/resolve.ts
+++ b/path/windows/resolve.ts
@@ -20,7 +20,7 @@ export function resolve(...pathSegments: string[]): string {
     // deno-lint-ignore no-explicit-any
     const { Deno } = globalThis as any;
     if (i >= 0) {
-      path = pathSegments[i];
+      path = pathSegments[i]!;
     } else if (!resolvedDevice) {
       if (typeof Deno?.cwd !== "function") {
         throw new TypeError("Resolved a drive-letter-less path without a CWD.");
diff --git a/path/windows/to_file_url.ts b/path/windows/to_file_url.ts
index a3d52c5857cff..f7f5ac3d4692e 100644
--- a/path/windows/to_file_url.ts
+++ b/path/windows/to_file_url.ts
@@ -20,10 +20,12 @@ export function toFileUrl(path: string): URL {
   if (!isAbsolute(path)) {
     throw new TypeError("Must be an absolute path.");
   }
-
   const [, hostname, pathname] = path.match(
     /^(?:[/\\]{2}([^/\\]+)(?=[/\\](?:[^/\\]|$)))?(.*)/,
   )!;
+  if (!pathname) {
+    throw new TypeError("Invalid pathname.");
+  }
   const url = new URL("file:///");
   url.pathname = encodeWhitespace(pathname.replace(/%/g, "%25"));
   if (hostname !== undefined && hostname !== "localhost") {