diff --git a/src/utils/filepath.test.ts b/src/utils/filepath.test.ts
index 5d6482e2d..875ef8cb7 100644
--- a/src/utils/filepath.test.ts
+++ b/src/utils/filepath.test.ts
@@ -56,6 +56,9 @@ describe('getFilePath', () => {
     expect(getFilePath({ filename: 'foo', root: 'bar', defaultDocument: 'index.txt' })).toBe(
       'bar/foo/index.txt'
     )
+
+    expect(getFilePath({ filename: 'filename.suffix_index' })).toBe('filename.suffix_index')
+    expect(getFilePath({ filename: 'filename.suffix-index' })).toBe('filename.suffix-index')
   })
 })
 
diff --git a/src/utils/filepath.ts b/src/utils/filepath.ts
index 1a2c2268b..f3f2ea82e 100644
--- a/src/utils/filepath.ts
+++ b/src/utils/filepath.ts
@@ -16,7 +16,7 @@ export const getFilePath = (options: FilePathOptions): string | undefined => {
   if (filename.endsWith('/')) {
     // /top/ => /top/index.html
     filename = filename.concat(defaultDocument)
-  } else if (!filename.match(/\.[a-zA-Z0-9]+$/)) {
+  } else if (!filename.match(/\.[a-zA-Z0-9_-]+$/)) {
     // /top => /top/index.html
     filename = filename.concat('/' + defaultDocument)
   }