diff --git a/packages/knip/src/plugins/netlify/helpers.ts b/packages/knip/src/plugins/netlify/helpers.ts
index 903e97370..c30b0d4e5 100644
--- a/packages/knip/src/plugins/netlify/helpers.ts
+++ b/packages/knip/src/plugins/netlify/helpers.ts
@@ -1,7 +1,6 @@
 import type { FunctionsConfig } from './types.js';
 
-export const validFunctionExtensions = () =>
-  ['.js', '.mjs', '.cjs', '.ts', '.mts', '.cts'].map(ext => ext.slice(1)).join(',');
+export const NETLIFY_FUNCTIONS_EXTS = 'js,mjs,cjs,ts,mts,cts';
 
 export const extractFunctionsConfigProperty = (config: FunctionsConfig, property: keyof FunctionsConfig) => [
   ...(config[property] ?? []),
diff --git a/packages/knip/src/plugins/netlify/index.ts b/packages/knip/src/plugins/netlify/index.ts
index 05c7f0960..9a65b93ee 100644
--- a/packages/knip/src/plugins/netlify/index.ts
+++ b/packages/knip/src/plugins/netlify/index.ts
@@ -2,7 +2,7 @@ import { join } from '../../util/path.js';
 import { timerify } from '../../util/Performance.js';
 import { hasDependency, load } from '../../util/plugin.js';
 import { toProductionEntryPattern } from '../../util/protocols.js';
-import { extractFunctionsConfigProperty, validFunctionExtensions } from './helpers.js';
+import { NETLIFY_FUNCTIONS_EXTS, extractFunctionsConfigProperty } from './helpers.js';
 import type { NetlifyConfig } from './types.js';
 import type { IsPluginEnabledCallback, GenericPluginCallback } from '../../types/plugins.js';
 
@@ -18,7 +18,7 @@ const CONFIG_FILE_PATTERNS: string[] = ['netlify.toml'];
 
 const ENTRY_FILE_PATTERNS: string[] = [];
 
-const PRODUCTION_ENTRY_FILE_PATTERNS: string[] = [`netlify/functions/**/*.{${validFunctionExtensions()}}`];
+const PRODUCTION_ENTRY_FILE_PATTERNS: string[] = [`netlify/functions/**/*.{${NETLIFY_FUNCTIONS_EXTS}}`];
 
 const PROJECT_FILE_PATTERNS: string[] = [];
 
@@ -37,7 +37,7 @@ const findPluginDependencies: GenericPluginCallback = async (configFilePath, opt
   ];
   const entryFiles = [
     ...extractFunctionsConfigProperty(localConfig.functions || {}, 'included_files'),
-    join(localConfig.functions?.directory ?? 'netlify/functions', `**/*.{${validFunctionExtensions()}}`),
+    join(localConfig.functions?.directory ?? 'netlify/functions', `**/*.{${NETLIFY_FUNCTIONS_EXTS}}`),
   ].filter(file => !file.startsWith('!'));
 
   return [...dependencies, ...entryFiles.map(toProductionEntryPattern)];