diff --git a/commands/gen.go b/commands/gen.go
index f3747722c..42b22165d 100644
--- a/commands/gen.go
+++ b/commands/gen.go
@@ -46,6 +46,8 @@ func newGenCommand() *genCommand {
 		style                  string
 		mode                   string
 		modeSelector           bool
+		classDark              string
+		classLight             string
 		highlightStyle         string
 		lineNumbersInlineStyle string
 		lineNumbersTableStyle  string
@@ -70,6 +72,8 @@ See https://gohugo.io/quick-reference/syntax-highlighting-styles/ for a preview
 					Style:                  style,
 					Mode:                   mode,
 					ModeSelector:           modeSelector,
+					ClassDark:              classDark,
+					ClassLight:             classLight,
 					HighlightStyle:         highlightStyle,
 					LineNumbersInlineStyle: lineNumbersInlineStyle,
 					LineNumbersTableStyle:  lineNumbersTableStyle,
@@ -91,6 +95,10 @@ See https://gohugo.io/quick-reference/syntax-highlighting-styles/ for a preview
 				_ = cmd.RegisterFlagCompletionFunc("mode", cobra.FixedCompletions([]string{"light", "dark"}, cobra.ShellCompDirectiveNoFileComp))
 				cmd.PersistentFlags().BoolVar(&modeSelector, "modeSelector", false, `scope selectors under a top level mode class, e.g. ".dark .chroma"`)
 				_ = cmd.RegisterFlagCompletionFunc("modeSelector", cobra.NoFileCompletions)
+				cmd.PersistentFlags().StringVar(&classDark, "classDark", "dark", `class name used by --modeSelector for dark styles`)
+				_ = cmd.RegisterFlagCompletionFunc("classDark", cobra.NoFileCompletions)
+				cmd.PersistentFlags().StringVar(&classLight, "classLight", "light", `class name used by --modeSelector for light styles`)
+				_ = cmd.RegisterFlagCompletionFunc("classLight", cobra.NoFileCompletions)
 				cmd.PersistentFlags().StringVar(&highlightStyle, "highlightStyle", "", `foreground and background colors for highlighted lines, e.g. --highlightStyle "#fff000 bg:#000fff"`)
 				_ = cmd.RegisterFlagCompletionFunc("highlightStyle", cobra.NoFileCompletions)
 				cmd.PersistentFlags().StringVar(&lineNumbersInlineStyle, "lineNumbersInlineStyle", "", `foreground and background colors for inline line numbers, e.g. --lineNumbersInlineStyle "#fff000 bg:#000fff"`)
diff --git a/markup/highlight/chromastyles.go b/markup/highlight/chromastyles.go
index c595c780a..f17170ad0 100644
--- a/markup/highlight/chromastyles.go
+++ b/markup/highlight/chromastyles.go
@@ -35,6 +35,12 @@ type ChromaStylesOptions struct {
 	// Scope selectors under a top level mode class, e.g. ".dark .chroma".
 	ModeSelector bool
 
+	// Class name used by ModeSelector for dark styles, defaults to "dark".
+	ClassDark string
+
+	// Class name used by ModeSelector for light styles, defaults to "light".
+	ClassLight string
+
 	// Foreground and background colors for highlighted lines, e.g. "#fff000 bg:#000fff".
 	HighlightStyle string
 
@@ -105,12 +111,19 @@ func ChromaStylesCSS(opts ChromaStylesOptions) (string, error) {
 		// them with a parent class on the page.
 		// There's no upstream option for this (I think), so do string replacements for now.
 		// TODO(bep) upstream option for this.
+		classDark, classLight := opts.ClassDark, opts.ClassLight
+		if classDark == "" {
+			classDark = "dark"
+		}
+		if classLight == "" {
+			classLight = "light"
+		}
 		var prefix string
 		switch style.Mode() {
 		case chroma.Light:
-			prefix = ".light "
+			prefix = "." + classLight + " "
 		case chroma.Dark:
-			prefix = ".dark "
+			prefix = "." + classDark + " "
 		default:
 			return "", fmt.Errorf("style %q does not have a light or dark mode", style.Name)
 		}
diff --git a/tpl/css/chromastyles_integration_test.go b/tpl/css/chromastyles_integration_test.go
index 402ef2ca6..682f11724 100644
--- a/tpl/css/chromastyles_integration_test.go
+++ b/tpl/css/chromastyles_integration_test.go
@@ -47,6 +47,25 @@ Light: {{ $light.RelPermalink }}|Dark: {{ $dark.RelPermalink }}|Default: {{ $def
 	b.AssertFileContent("public/css/chroma.css", "/* Background */ .bg {", "background-color:#272822")
 }
 
+// See issue 15167.
+func TestChromaStylesCustomModeClasses(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableKinds = ["taxonomy", "term", "rss", "sitemap", "section", "page"]
+-- layouts/home.html --
+{{ $light := css.ChromaStyles (dict "targetPath" "css/chroma-light.css" "style" "github" "mode" "light" "modeSelector" true "classLight" "theme-light") }}
+{{ $dark := css.ChromaStyles (dict "targetPath" "css/chroma-dark.css" "style" "github" "mode" "dark" "modeSelector" true "classDark" "theme-dark") }}
+Light: {{ $light.RelPermalink }}|Dark: {{ $dark.RelPermalink }}|
+`
+
+	b := hugolib.Test(t, files)
+
+	b.AssertFileContent("public/css/chroma-light.css", ".theme-light .chroma ", ".theme-light .bg {")
+	b.AssertFileContent("public/css/chroma-dark.css", ".theme-dark .chroma ", ".theme-dark .bg {")
+}
+
 // Chroma's minifier drops token rules whose color equals the style's default
 // foreground (e.g. .nx in github-dark). In a paired light/dark setup the light
 // sheet's explicit rule would then leak into dark mode, so these must be re-emitted.