diff --git a/internal/lint/code.go b/internal/lint/code.go
index 07ae7260..6db7ab58 100755
--- a/internal/lint/code.go
+++ b/internal/lint/code.go
@@ -42,7 +42,7 @@ func (l *Linter) skipsComment(scope string) bool {
 }
 
 func (l *Linter) lintCode(f *core.File) error {
-	lang, err := code.GetLanguageFromExt(f.RealExt)
+	lang, err := code.GetLanguageFromExt(f.NormedExt)
 	if err != nil {
 		// No tree-sitter grammar available for this file type.
 		return l.lintCodeOld(f)
diff --git a/internal/lint/data.go b/internal/lint/data.go
index d0e1cfb2..48b6ca08 100644
--- a/internal/lint/data.go
+++ b/internal/lint/data.go
@@ -106,7 +106,7 @@ func (l *Linter) lintData(f *core.File) error {
 // lintDataComments lints the comments of a data file that has a grammar --
 // YAML or TOML -- and does nothing for one that has no comments to read.
 func (l *Linter) lintDataComments(f *core.File) error {
-	if _, err := code.GetLanguageFromExt(f.RealExt); err == nil {
+	if _, err := code.GetLanguageFromExt(f.NormedExt); err == nil {
 		return l.lintCode(f)
 	}
 	return nil
diff --git a/testdata/e2e/lint.yaml b/testdata/e2e/lint.yaml
index fff2649a..644ecf92 100644
--- a/testdata/e2e/lint.yaml
+++ b/testdata/e2e/lint.yaml
@@ -1852,6 +1852,82 @@ cases:
       test.pl:5:21:vale.Annotations:'XXX' left in text
       test.pl:8:7:vale.Annotations:'TODO' left in text
 
+  - name: perl-format-mapping
+    about: a `.nix` file has no grammar, so under `nix = pl` Vale reads its
+      comments as Perl comments
+    files:
+      .vale.ini: |
+        StylesPath = styles
+        MinAlertLevel = suggestion
+
+        [formats]
+        nix = pl
+
+        [*]
+        T.Tok = YES
+      styles/T/Tok.yml: |
+        extends: existence
+        message: "'%s' found"
+        level: error
+        tokens:
+          - ZQX
+      default.nix: |
+        # A ZQX in a comment.
+        { value = "ZQX"; }
+    args: default.nix
+    exit: 1
+    want: |
+      default.nix:1:5:T.Tok:'ZQX' found
+
+  - name: perl-ext-flag
+    about: a `.nix` file has no grammar, so under `--ext=.pl` Vale reads its
+      comments as Perl comments
+    files:
+      .vale.ini: |
+        StylesPath = styles
+        MinAlertLevel = suggestion
+
+        [*]
+        T.Tok = YES
+      styles/T/Tok.yml: |
+        extends: existence
+        message: "'%s' found"
+        level: error
+        tokens:
+          - ZQX
+      default.nix: |
+        # A ZQX in a comment.
+        { value = "ZQX"; }
+    args: "--ext=.pl default.nix"
+    exit: 1
+    want: |
+      default.nix:1:5:T.Tok:'ZQX' found
+
+  - name: ext-flag-overrides-grammar
+    about: "`--ext=.c` parses a `.ts` file as C even though TypeScript has a
+      grammar, so `//` in a template literal starts a comment"
+    files:
+      .vale.ini: |
+        StylesPath = styles
+        MinAlertLevel = suggestion
+
+        [*]
+        T.Tok = YES
+      styles/T/Tok.yml: |
+        extends: existence
+        message: "'%s' found"
+        level: error
+        tokens:
+          - ZQX
+      test.ts: |
+        const s = `// ZQX in a template literal`;
+        // ZQX in a comment.
+    args: "--ext=.c test.ts"
+    exit: 1
+    want: |
+      test.ts:1:15:T.Tok:'ZQX' found
+      test.ts:2:4:T.Tok:'ZQX' found
+
   - name: php
     args: test.php
     exit: 0
diff --git a/testdata/e2e/views.yaml b/testdata/e2e/views.yaml
index 421c4085..b991fe13 100644
--- a/testdata/e2e/views.yaml
+++ b/testdata/e2e/views.yaml
@@ -498,3 +498,34 @@ cases:
       site.yml:1:7:Vale.Spelling:Did you really mean 'defalt'?
       site.yml:2:23:Vale.Spelling:Did you really mean 'storag'?
       site.yml:3:29:Vale.Spelling:Did you really mean 'trailng'?
+
+  - name: data-comments-format-mapping
+    about: a `.conf` file has no grammar, so under `conf = yml` Vale reads its
+      comments as YAML comments
+    files:
+      .vale.ini: |
+        StylesPath = styles
+        MinAlertLevel = suggestion
+
+        [formats]
+        conf = yml
+
+        [*.conf]
+        BasedOnStyles = Vale
+        Vale.Terms = NO
+        Vale.Avoid = NO
+        Vale.Repetition = NO
+        View = Data
+      styles/config/views/Data.yml: |
+        engine: dasel
+        scopes:
+          - name: title
+            expr: title
+      site.conf: |
+        # The defalt settings.
+        title: A guide to the storag layer
+    args: site.conf
+    exit: 1
+    want: |
+      site.conf:1:7:Vale.Spelling:Did you really mean 'defalt'?
+      site.conf:2:23:Vale.Spelling:Did you really mean 'storag'?