diff --git a/d2themes/sketch_overlay.go b/d2themes/sketch_overlay.go
index 65ccde356..abe9912f1 100644
--- a/d2themes/sketch_overlay.go
+++ b/d2themes/sketch_overlay.go
@@ -24,18 +24,11 @@ func (o *ThemableSketchOverlay) Render() (string, error) {
 	if color.IsThemeColor(o.fill) {
 		o.el.ClassName += fmt.Sprintf(" sketch-overlay-%s", o.fill) // e.g. sketch-overlay-B3
 	} else {
-		var lc string
-		if color.IsUrlGradientId(o.fill) {
-			lc = "normal"
-		} else {
-			var err error
-			lc, err = color.LuminanceCategory(o.fill)
-			if err != nil {
-				return "", err
-			}
+		lc, err := color.LuminanceCategory(o.fill)
+		if err != nil {
+			return "", err
 		}
 		o.el.ClassName += fmt.Sprintf(" sketch-overlay-%s", lc) // e.g. sketch-overlay-dark
 	}
-
 	return o.el.Render(), nil
 }
diff --git a/lib/color/color.go b/lib/color/color.go
index cbd8971f7..fccb2a79c 100644
--- a/lib/color/color.go
+++ b/lib/color/color.go
@@ -86,6 +86,9 @@ func darkenCSS(colorString string) (string, error) {
 }
 
 func LuminanceCategory(colorString string) (string, error) {
+	if IsURLGradientID(colorString) {
+		return "normal", nil
+	}
 	l, err := Luminance(colorString)
 	if err != nil {
 		return "", err
diff --git a/lib/color/gradient.go b/lib/color/gradient.go
index 6b308b440..51dbde637 100644
--- a/lib/color/gradient.go
+++ b/lib/color/gradient.go
@@ -247,8 +247,8 @@ func IsGradient(color string) bool {
 	return GradientRegex.MatchString(color)
 }
 
-var UrlGradientId = regexp.MustCompile(`^url\('#grad-[a-f0-9]{40}'\)$`)
+var URLGradientID = regexp.MustCompile(`^url\('#grad-[a-f0-9]{40}'\)$`)
 
-func IsUrlGradientId(color string) bool {
-	return UrlGradientId.MatchString(color)
+func IsURLGradientID(color string) bool {
+	return URLGradientID.MatchString(color)
 }