diff --git a/cli/run/loadConfigFile.ts b/cli/run/loadConfigFile.ts
index 70addb40dce..8f8c98ee534 100644
--- a/cli/run/loadConfigFile.ts
+++ b/cli/run/loadConfigFile.ts
@@ -103,12 +103,19 @@ async function getDefaultFromTranspiledConfigFile(
 	return loadConfigFromBundledFile(fileName, code);
 }
 
+function isSamePath(fileName1: string, fileName2: string): boolean {
+	if (process.platform === 'win32') {
+		return fileName1.toUpperCase() === fileName2.toUpperCase();
+	}
+	return fileName1 === fileName2;
+}
+
 async function loadConfigFromBundledFile(fileName: string, bundledCode: string): Promise<unknown> {
 	const resolvedFileName = await fs.realpath(fileName);
 	const extension = extname(resolvedFileName);
 	const defaultLoader = require.extensions[extension];
 	require.extensions[extension] = (module: NodeModule, requiredFileName: string) => {
-		if (requiredFileName === resolvedFileName) {
+		if (isSamePath(requiredFileName, resolvedFileName)) {
 			(module as NodeModuleWithCompile)._compile(bundledCode, requiredFileName);
 		} else {
 			defaultLoader(module, requiredFileName);
diff --git a/scripts/load-perf-config.js b/scripts/load-perf-config.js
index 647ee9b720f..24a1dcce432 100644
--- a/scripts/load-perf-config.js
+++ b/scripts/load-perf-config.js
@@ -28,7 +28,7 @@ exports.loadPerfConfig = async () => {
 function loadConfigFromCode(code) {
 	const defaultLoader = require.extensions['.js'];
 	require.extensions['.js'] = (module, filename) => {
-		if (filename === configFile) {
+		if (rollup.isSamePath(filename, configFile)) {
 			module._compile(code, filename);
 		} else {
 			defaultLoader(module, filename);
diff --git a/src/utils/path.ts b/src/utils/path.ts
index 223db42fba7..bc94298a59b 100644
--- a/src/utils/path.ts
+++ b/src/utils/path.ts
@@ -15,4 +15,11 @@ export function normalize(path: string): string {
 	return path.replace(BACKSLASH_REGEX, '/');
 }
 
+export function isSamePath(fileName1: string, fileName2: string): boolean {
+	if (process.platform === 'win32') {
+		return fileName1.toUpperCase() === fileName2.toUpperCase();
+	}
+	return fileName1 === fileName2;
+}
+
 export { basename, dirname, extname, relative, resolve } from 'path';
diff --git a/src/utils/sanitizeFileName.ts b/src/utils/sanitizeFileName.ts
index 26c0b328dad..a1e6f88178d 100644
--- a/src/utils/sanitizeFileName.ts
+++ b/src/utils/sanitizeFileName.ts
@@ -1,7 +1,7 @@
 // https://datatracker.ietf.org/doc/html/rfc2396
 // eslint-disable-next-line no-control-regex
 const INVALID_CHAR_REGEX = /[\x00-\x1F\x7F<>*#"{}|^[\]`;?:&=+$,]/g;
-const DRIVE_LETTER_REGEX = /^[a-z]:/i;
+const DRIVE_LETTER_REGEX = /^[a-zA-Z]:/i;
 
 export function sanitizeFileName(name: string): string {
 	const match = DRIVE_LETTER_REGEX.exec(name);